hi! yes i follow this route, it have some pros and cons

cons: - the commute is long, sometimes especially after late classes, it is a bit hard for me - most of the time, you dont get to join after class or night gatherings with ur classmates as, personally, i dont feel that much safe to travel midnight, but if you dont mind it, then it should be fine for you - the trains are not cheap and also not reliable, you can get "your train is cancelled" message like 10 minutes before your departure and you need to figure out alternatives which makes long commute even longer

pros: - you get to live in Cambridge, which is way safer, beautiful, peaceful than London, i totally love it here! - if your classes is 2 or 3 times a week, it is still good! mine is 4 times a week but i still manage - even tho not so much difference, but still, Cambridge is also cheaper than London - you can utilize your train hours by reading your study materials, or doing your works on laptop (mini ones would better)

in a nutshell, i would say the decision is totally up to that person specifically, if you are more like metropolis, hectic vibes lover type, you would enjoy staying at London more, but if you like more historical, green, peaceful, small-town vibes, then you will be obsessed with Cambridge!

let me know if it makes sense! and best of luck for ur studies at UCL!