Body was dark with very pale/narrow yellow markings and the eyes were very strange - quite fly-like. It was 2.5cm to 3cm long so quite big - almost the size of a carpenter bee.
I live in the west highlands if that's of any help.
Yes, that's definitely a hover fly (syrphid). They mimic bees, but are completely harmless. In fact, they do a lot of good, feeding on aphids and rotten food. They also pollinate flowers.
You can tell the difference between these and bees by their large rounded eyes and the fact that they only have 2 wings. They won't sting you, and are good things to have in the summer garden.
Thank you all so much for your responses. I've now found some great images online which are almost identicle and I'm sure he was a hover fly. The first one I've [knowingly] seen here. I've been looking around for him again today but he's not here so I think my wall was just a rest stop.
Zacsmaster: please apologise to your entymology friend for my bad photograph - I'm sorry it looked like a horsefly - we get lots of them and call them cleggs locally - I've been bitten a few times - they really are nasty. It definitely wasn't one of them - I think in my haste to take a pic I may have jiggled the camera a bit, but thank you so much for going to the trouble of investigating for me.
but are you aware how many types of horse flies there are? Nine at least and your photo looks very much like Tabanus Sudeticus- one variety of horse fly. On the wing July Aug in grassland and open woodland.
Now I've looked at all your links and photos I'm convinced that he is maybe a type of horsefly after all - just one I've not seen before. He was a big beast.
Thank you all so very much for taking the trouble to help me out and apologies again to Zacsmaster and his friend - I wasn't doubting you, just matched him to the hoverfly photos I already had.