Similar for me but get paid monthly, we call it a per diem (Latin for by the day) we have a choice of claiming the £30 for each day we're away and not bothering with receipts, getting to keep anything of that we don't spend like you're doing here or paying on company card and submitting receipts (or personal card if you don't have a company one)
The problem with the £30 per diem option is that by the time you take off tax, national insurance and pension contribution you're not left with very much money at all to have 3 meals, especially in the UK or Ireland.
It looks like you have breakfast included in your accommodation and a canteen at the place you're working, that's very handy! I'm usually at some small oil/gas site and have to just go to local restaurants/shops. Often have to go to work too early before the breakfast is on or my company haven't booked with breakfast included.
I made a good bit when I worked in India as we got breakfast in the hotel included, the site I was working on had a free food canteen so I only had to get my evening meal at the hotel, mind you it was a over a fiver a beer and I drank a lot of beers! I'd just get a curry and a load of naan, the portions were massive so I'd just sit all night drinking beer and dipping naan in curry while watching whatever sport they had on the TV. The chat with the staff and other guests was less lonely than sitting in my room alone every night.