As stated above, only with ATC clearance, as it's Class C above FL195 across all of the UK (and Europe).
Here's an extract from the CAA website:
Civil VFR flights at and above FL195, up to and including FL285, will only be authorised in an airspace reservation or in accordance with the authorisation procedures published in the UK AIP. Civil VFR flights wishing to operate above FL285 will only be permitted in an airspace reservation.
Have a read of
http://www.caa.co.uk/docs/1239/Frequ...0Questions.pdf