A lot depends on surrounding terrain amongst other factors.
Take a look here :-
https://ukrepeater.net/maps.html
From there you can select which band, select a repeater and then look at its specific details including coverage maps.
Not all the repeaters have exact locations or maps with the keepers having the details private due to past thefts, acts of vandalism etc.
Some of the coverage maps are from real data and/or computational but pretty accurate. Tropospheric lift conditions can extend those ranges much further, for instance GB3PI often experiences opening to Wales and Northern England on a fairly frequent basis with morning temperature inversions extending the range on 2m too. These 'lifts' can also be found on 70cm but experienced less frequently.
Hope that helps,
Victor