Buy first then sell. Is it possible?

[Deleted User]

I'm looking to buy a larger house in the region of 350-400k in the next two-three months. I've got up to 90k as a deposit and earn about 44k gross. I also currently own my own place outright (worth about 150-160k), but it needs a bit of renovation before I sell it. This would be much easier to accomplish if I move out first. I'm not keen on rented accommodation, so I've been thinking of buying first, organising the work and then selling my old house after the work's completed.

Would mortgage providers be willing to lend higher salary multiples, on the understanding that as soon as I sell my place I would use the proceeds to pay off part of the mortgage; i.e. I would temporarily need between 7 and 8x salary, but in a few months would reduce it to less than 4x salary. I know the first few months payments would be higher than I would wish, leaving only about £500 of disposable income per month, but family are willing to help out in the short term. Parents are also willing to act as guarantors if necessary, but would rather not drag them into it if not required.

Has anyone had any experience doing this sort of thing? Is there another easier or better way of achieving this?