Toby
Some advice XCweather is using the ECMWF Airport Data from all the various UK airports - and then configuring it in their own interface and then time stamping it as "Current Time" - in fact the data can often be 4 hours out - that said it's still good at giving an overall picture of the whole of the UK - but will not be, like WindGuru etc able to differentiate for local weather patterns which is normal in the warmer months.
Along various parts of the UK South Coast from Portsmouth to Brighton, actual wind can vary by at least 12knts from one location to another - this is due to the local thermal (sea breezes) that occur this time of year - at
http://www.seaspritesports.com/weatherframe.htm there you'll see actual weather updating every minute, from one of the "windiest" locations together with links to Hayling & Shoreham and others so you can compare the actual wind.
REgards
WC