Oh dear, I am sorry to hear that. You must get 3 quotes. I had the back roof done last summer and it was £6,000. that included stripping down to rafters. New breathable felt, tanalised battens etc. So sorry to be the bearer of bad news. The problem is that since Covid the prices of all materials has gone up so much.
Something that was £10 is now £20 in the building industry. I have just has three quotes to remove the tile- hung side to my bungalow, so not much. Tiles, £6,000. Plastic cladding £2,600. Sadly, I am not in a position to say leave it for a couple of years. It is URGENT. Good luck, but get more quotes and thoroughly question it. Mrs Bouquet