Bit of a mystery with a recently bought mk1 03 Focus 1600

After low fuel light came on I parked it up and on restarting it had no power in forward gears then wouldn't start at all so put a can of petrol in gauge read just under a quarter full .

RAC diagnosed it to be coil but after cleaning plugs and a little fiddle with the cam sensor lead it started and ticked over fine on 800 revs though temp gauge came up to half pretty quick (after 4 mins)

though started still total loss of power when in gear / pull away, though fine in reverse.

RAC "richard" (lovely bloke) put a new coil on to try that and no joy so put old one back on. ended up towing.

He did say pos ECT sensor but also said that the whole thing seemed "very strange" as diagnostics was saying coil

started 1ST time this morning but seemed to have a lot of "condensation" (thoughts went to head gasket) coming out of exhaust. so checked water level and clour and everything seemed fine

any answers would be greatly appreciated