Mortgage on universal credit unfair than rent

Hi @wozzer and welcome to the community. I'm sorry they made you feel like a criminal. If you have over £6,000 in savings, UC will take a small amount each month from your payment:

"Your payments will be reduced by £4.35 for every £250 you have between £6,000 and £16,000. Another £4.35 is taken off for any remaining amount that is not a complete £250."

This means that you can save for necessary home repairs or anything else you need as long as your savings don't go above £16,000. I hope this helps.