I did my valve clearances yesterday and it is a very simple task with the Omicron adjusting tool. Annoyingly the crank pully nut it obscured by the radiator but you can just get a large spanner on it allowing about 1/10 of a turn a time. Take the plugs out t0 make turning easier. I took the distributer cap off and positioned the rotor arm to #1 so it was at TDC and started with that one. One is spoilt for choice. One can either use the feeler gauge in the gap below the tappet or between the tappet and the little push rod or even the gap at the cam heel. Just make sure the cam lobe is the opposite side.
The omicron tool is only a few quid and brilliantly simple, although for the easiest solution is to have 3 hands, for me a bottle of my wife's favorite sauvignon blanc was a good investment. All my clearances were .05mm tight, I should check them more often.