Well it was double glazing, new bathroom, flooring and new kitchen. The reason I didn't include the costs in the year of expenditure was because I was going to sell the property and claim the costs against CGT on disposal.
That sounds a bit cavalier. Firstly you need to decide whether this expenditure was capital or not. You can't just claim it against income or capital to suit your needs or to gain the best tax advantage.
If it was indeed a revenue expense for 2009-10, then you have until 31-01-2012 to amend that year's tax return and claim the deduction. But don't be surprised if HMRC then enquire into that amendment. And you can't claim it in your 2010-11 tax return, as it does not relate to that year.