I thought I'd keep the question simple by sticking to the legal/technical question only, but then there are no simple questions in aviation, are there!
I'm a lapsed PPL/IR MEP, with several years of regular IFR flying throughout Europe. My home base was a quiet international airport in class D airspace. I would regularly file IFR and fly SID - airways - STAR- IAP, even in good VMC, because I enjoyed it, because it was, frankly, easier, and to stay in practise for when I needed it. I always enjoyed flying IFR, particularly in real IMC, and was able to develop my skills to the point where I could do this well, and remain fully relaxed. Having also gone through the process of being a nervous newbie, completely maxed out, and way 'behind' the aeroplane, I am fully able to appreciate the difference.
The question occurred to me, with all my ratings having lapsed, that I might be able to re-engage with my old skills, by practising an approach in good VMC. Since most of my flying was done with a current IR, the question of being able to accept an IFR clearance was never an issue, and I realised I didn't know if you could fly a procedure with a VFR clearance.
I certainly take the point about maintaining a good lookout, but one can make a reasonable judgement based on all the individual circumstances.
Thanks for all the replies - much appreciated