If you want to move outside of West Berkshire by mutual exchange, these sites may help you.
Free exchange services
Community Council House Exchange
UK-wide database and forum
Council House Exchanges
UK-wide database and forum, broken down by region
Exchange UK
UK-wide database and forum
Houseswap Forum
UK-wide database, restricted free access with option to pay for enhanced services
Paid for exchange services
UKhomeswap
Exchange Homes
Homeswapper
Launched in February 2007, it's currently a free service but will be charging in the future