The damp course and associated costs are capital enhancement as may be the Kitchen as there was not a fitted kitchen there before as it sounds like a substantial upgrade. I would claim that as an enhancement so it increases thew base cost by the amount spent. Decoration, carpets, flooring are revenue in nature so can not be claimed. Basically :
These can be reclaimed under ICTA88/S401 or ITTOIA05/S57.
Relief is only due where the expenditure:
(1) is incurred within a period of seven years before the date the rental business is started, and
(2) is not otherwise allowable as a deduction for tax purposes, and
(3) would have been allowed as a deduction if it had been incurred after the rental business started.
This means that, to be allowable, the expenditure must be incurred wholly and exclusively for the purposes of the rental business and must not be capital expenditure etc.
http://www.hmrc.gov.uk/manuals/pimmanual/
http://www.hmrc.gov.uk/manuals/pimmanual/PIM2505.htm
Regards Peter