One thing to keep in mind with these loans is that they are variable, based on 3% over the BoE base rate. For a loan taken out next year, maturing in 2026, it would *not* be safe to assume the base rate will stay at 0.5% for that whole time because it has been at an historic low. This site shows the rates since 1975:
http://www.bankofengland.co.uk/boeapps/iadb/repo.asp
http://www.bankofengland.co.uk/boeapps/iadb/repo.asp
The average over that period is 9.6% (!) and it peaked at 17% in 1979. I’m not saying it is likely to go that high any time soon, but over the ten year loan period it could certainly get back to 3-5% or more (+ the 3% margin).
That would increase the monthly payments quoted in the BBVA example by ~10-20%, as well as the total interest paid. Probably still manageable but you want to sign on the dotted line with your eyes open to avoid a surprise later on (in the form of a rate increase notification from the bank, just after you purchased the Brietling and the Aston ;-).