Okay, so I ended up with 3 sets of pedals, the Wellgo flat/SPD combis and 2 x Shimano 520's. I also bought a pair of Northwave Mission ATB cycling shoes.
The three sets of pedals, plus the accompanying cleats and the Northwave shoes will be going up for sale. I officially hate being clipped in and have reverted to flat pedals. I'll live with being a little less efficient.
Yes I gave them a fair go, no problems unclipping and only some initial probs clipping in. 200 miles and all I've managed is to hurt my knee and keep myself off the bike, plus I fell over. Typical clipless moment and all that, but I'd rather not fall over.....ever. Could feel a slight benefit when climbing out of the saddle. For me the cons outweighed the pros, I didn't experience any 'light and day' difference over flat pedals.
I'm sure that getting a better stroke, pedalling in circles, and getting the cleats set right would have helped. But I just don't see enough benefits, I like being able to get on any bike, with any shoes. If I ever plan on racing, or strenuous events, then I might reconsider. but, for my purposes, flats will be fine.