How does it actually work? If I got £100k mortgage and give them £10k deposit, do they then give me the £100k to buy a house with and the £10k pays off a large part of the projected interest, or do I have £110k to buy the house with and the £10k is just their buffer if I mess up and have to sell the house quickly?
you buy the house for 110k
and the 10k is the buffer, but you need another 3k approx to pay for 'stuff'.
if you pay 110k and then the property value drops below 100k then you can't change lender and you can't sell.
So then the lender can do with you as it pleases.
Also during the lifetime of the loan interest rates will go up and can be expected to average up to 8%. It's all in the lap of the gods. But because you have magically become a 'high' risk they will have a very special high rate for you.