Currency gains

I wonder if any Taxation readers can provide some advice on the following topic.

A gain on foreign currency acquired by an individual for personal expenditure outside the UK (including the provision or maintenance of any residence outside the UK for himself his family or dependants) is not a chargeable gain (TCGA 1992 s 269).

Is this still the position where UK taxed funds are transferred for the purpose of extending and improving a property in the United States of America and the funds are held in a US dollar account for a significant period of time while the work is undertaken?

We have a client in these circumstances and this has resulted in a currency gain of more than £250 000.

Two further thoughts occur to me that might be relevant.

First does a significant time delay on realisation change...