Cracked on with the job today. Thanks to Limey Linda and Hightower for their advice.
I placed a piece of wood behind the arm to hold it in place. This had to be replaced three times as the gap got bigger. Then I started to gently tap the bolt with a lump hammer, using another bolt to give me some space. Once it started to move I applied gentle heat from a paint stripper. It took two hours of gentle tapping to get the arm off. That bit was thanks to Limey Linda. Checking on the opposite side of the steering I soon realised I would have to undoe that as well. Cheers Andy for reminding me. Could have caused some expensive damage without that bit of advice. Another hour later all was greased up and reassembled
So now looking forward to the 25th