As are you clearly with your grasp of mortgages I'm like many going to get hammered come next renewal thanks to Truss and friends.
Due to circumstances (the ex) I have ended up with 16 years left to pay mine off, I took 3 x plus the Wife's income, affordability testing meant I had to be able to afford it at 6.5 percent, whilst I'm fortunate that I can afford the payments it is still a turd sandwich created by Liz and friends and let us not forget greedy retailers, petrol suppliers pushing up inflation.
Kids now have very little chance of getting on the property ladder, 250 grand for a 2 up 2 down round here 😲 gone are the days when you could get a 3 bed semi for 43 grand like I did for my 1st house. Only way is bank of Mum and Dad and sadly I'm in no position to help much, you are lucky that you could help yours. I can see people ending up with lifetime mortgages that you leave to the next generation like in some other countries.