Nearly all renovation projects are different from one another so finding a common approach to the costs is difficult. The only sure way is to obtain estimates from tradesmen for various parcels of work, but this is not really practical when you don’t yet own the house.

One method is to start with a new work figure of, say, £900 per m2 and then deduct 40 per cent for the items that don’t need upgrading (usually the external walls, floors and roof) to produce a figure of £540 per m2 for the work.

If the building is in a reasonable state and items such as plumbing, heating and electrics are OK, I would increase the percentage to 60 per cent to give a figure of £360 per m2.

This is a rough and ready approach but at least it should produce a budget figure that you can adjust as more information becomes available.