Which bolt? I used a quarter inch ratchet (6 inches long) and a 2inch extension, but just used that to break the bolts loose. Then took the extension off the ractchet and just turned the extension by hand to get the bolt fully out.
I would get a really secure fitting (bit fully into the bolt head and nice and tight) and then use force. Saying that, you DONT want to round off the head - which is why I put emhphasis on the secure bit.
Out of interest where in the uk are you?