My recollection of the 'who gives way' thing is that the vehicle encroaching into the other vehicles lane gives way, and where there's no centre line the centre of the road serves that purpose. On single-track roads whilst the old cyclist mentioned above is correct, the preamble bit means that as often as not the cyclist ends up giving way. Rule 155 of the H.C. specifically refers to single-track roads, I only tend to assert the other drivers obligation to give way when I'm going up hill and stopping would be a P.I.T.A.