Question: If you move money into a sterling account or whatever, and it appreciates against the euro,and you then withdraw it/ convert it back to euros etc, is this a capital gain, or how does this work?
Yes, that would lead to a capital gain. Depending on how much money you transferred any gain might be below your €1270 annual exemption.
If you are already in this situation, remember CGT on gains realised between 01/01/2011 and 30/11/2011 is due by 15/12/2011.