Conservation bodies such as English Heritage say out-of-character improvements can actually de-value a house.
Stone cladding seems to provoke most outrage (Planning Permission is now necessary), followed by replacement doors and windows.
Double-glazing is the most popular improvement, but unless the windows need replacing anyway,
it can be one of the least cost-effective; the capital cost could take 15 years or longer to recoup through energy savings.
Using sympathetic materials to retain or enhance the character of your property is likely to pay dividends,
so avoid substituting a Welsh slate roof - serviceable after some remedial work - with cheap cement-tiles.
Where it is practical, put back original features like cornices, fireplaces, railings and dado and picture rails.
The standard of workmanship is an obvious factor and a job well-done is clearly better than a shoddy cowboy job or a botched-up DIY solution,
so choose your contractor carefully.
The HomePro process will help you find a vetted professional to take on the project under the terms that suit you.
to go to the Find a Pro service.
For larger projects, it may be worth appointing a chartered surveyor or architect to supervise the work.
These normally charge 10-15% of the contract sum, but will often haggle with builders to reduce the tender price.