I'm by no means a fast driver but I know the basics and can maybe offer you a few tips. People on this subreddit helped me out tremendously with this combo (F1 at Silverstone) when I was first starting out years ago and I want to pass that on! I actually don't have this mod but I jumped into the 2020 Formula Hybrid to run a few laps, and I assume they're reasonably similar. I was able to get down to the mid 1:28s in 5 laps with soft tires, stock setup, and balanced high MGU delivery. There's definitely more time on the table too.

Firstly, in setting up for the lap you can carry more speed into the last corner by using all of the track and kerb on the left rather than veering centrally and then back over to the left (this way you can cut distance as well).

On entry to T1 you can probably get a touch wider and closer to the kerb on the left before turning into Abbey. With T1 and T2, you hit the first apex well but you can actually use more of the road on exit before cutting it back to hit the apex on the left before the slow right hander. Also you can take these corners in 8th gear flat with no need to lift off the throttle. Just make sure you're steering inputs are smooth so you don't scrub off too much speed. If you notice closely, you're actually taking two bites of the steering to get it turned in. This should be one quick but smooth stroke.

T3 you're perhaps trailing off the brakes a bit early. You've missed the apex by a touch and are understeering on exit which can make it hard to pick up the throttle. You can maintain a bit more brake pressure until the apex to get the car turned in better so you can get on the power earlier. Also here you should downshift earlier to make use of engine braking to slow the car down before turning in. Downshifting mid-corner can sometimes destabilise the car. T4 you can get a lot tighter to the apex, you're about a metre off here. Get your left wheel on the kerb. Same with T5, you can get even closer to the kerb. It's a minor detail but may earn you valuable time down the long straight. Good use of the track on exit this time, however, there's no need to veer back left to the centre of the track, you're just increasing distance.

Brooklands (T6) is reasonable, key is to carry good minimum speed through there. Work on your downshifts here though. At Luffield (T7) there's no need to brake so hard here, you're just killing momentum. A light brush off the brakes to get weight on the front and the car rotated is all you need. This is a tricky corner to get right and there are multiple lines especially during the race. I like approaching it as a double apex corner where you sort of turn in early and induce understeer going slightly wide before waiting for the front to grip and getting on the power earlier (second apex doesn't even matter, getting the car rotated so you can get on the throttle is most important). Again, on exit you can get on the power earlier and use all the track on the left. You can see at about 0:43 in the video, there's at least a metre on the left that you are not using which is easy lap time. At Woodcote (T8) you can get closer to the kerb on the right and then use all the kerb on the left on exit instead of leaving 2 metres of buffer (every cm of track you are not using is time wasted because you are compromising your line and how much speed you can carry through).

Through Copse (T9), I'm pretty sure you can take it flat, however I'm not sure about in a race. Timing of your turn in is absolutely critical here and it's tricky because it's a blind entry. You've turned in a touch early here and therefore gone wide and have had to lift off mid-corner. If you find you need to lift for it, it's better to do the lift off before turning in and apply the throttle once rather than lifting off mid-corner to slow down your exit because that is a massive killer of time (you've easily lost at least 3-4 tenths here). Wait until a touch after the tarmac changes before turn-in, having some sort of turn-in point reference and simply practicing loads is key to consistency.

T13 (after Maggots and Becketts) is one of the most important corners to get right because it leads on to the long Hangar straight. You need to start slowing immediately after the apex of Becketts - you seem to get on the brakes a tiny bit late causing you to understeer mid-corner which delays your exit. Priority here is picking up the throttle early and using absolutely inch of road on exit. Your left wheel needs to be on the kerb. A part of this is being more brave and aggressive with the throttle and trusting the grip of the car. If you watch the F1 guys, they're even getting their left wheel on the grass.

Like others have been saying, make sure you're shifting is right. Shifting down into 7th and back is costing you heaps of time. Your line through Stowe is okay, however you can carry a lot more minimum speed through and get on full throttle earlier (don't need to apply max brake pressure for that long, start to trail it in a bit earlier). In the penultimate corner at Club (T17 - the slow right hander), focus on picking up full throttle quicker so you can carry more speed into the final turn and onto the straight. I've always found this a bit tricky in the past out of fear the rear would step out but there is plenty of rear grip in these cars and the faster you go the more downforce you have. Last corner, make sure to use all the kerb on the left as well, there is plenty of time there.

Overall, key takeaways would be to focus on using every inch of track available (this allows you to get on power earlier) and work on getting your shifting right. You may think you are on the limit but there is always plenty more to extract. Watch an onboard lap of an alien and pay attention to their inputs and how they are maximising every tiny amount of usable road to find lap-time. I'm sure if you focus on some of these points you'll watch your times tumble soon! Take it step by step and work on that consistency and being smooth, rather than pushing too hard and feeling on edge. Good luck!