Thanks for all the replies.
From a legal point of view, here is my take on this:-
Rule 17 (7) (b) states:-
A flying machine or glider may not land on a runway at an aerodrome if the runway is not clear of other aircraft unless, in the case of an aerodrome having an ATCU, that unit otherwise authorises.
Rule 1 (1):-
"runway" means an area, whether or not paved, which is provided for the take-off or landing run of aircraft;
Runway dimensions are defined in the AIP, so if the runway is physically clear of "other aircraft" then one "may" land.
Now I am aware that Rule 43 (2) (a) "Markings for paved runways and taxiways" states...
two yellow broken lines and two continuous lines, as illustrated...., signify the holding position closest to the runway beyond which no part of a flying machine or vehicle shall project in the direction of the runway without permission from the ATCU..... .....where there is no ATCU at the aerodrome the markings signify the position closest to the runway beyond which no part of a flying machine or vehicle shall project in the direction of the runway when the flying machine or vehicle is required by virtue of Rule 37 (3) (a) of these Rules to give way to aircraft which are taking off from or landing on that runway.
End of legal epistle!
I am not advocating a campaign to land (or take off from) a runway where it is not safe to do so but, for example, in the case where I am landing at an aerodrome (with no ATCU) behind another aircraft and I can see that the preceding aircraft has physically cleared the runway (albeit but has yet to clear the holding point lines) then I see no (legal) reason why I should not proceed and land. Indeed to lend more weight to this it is highly probable at an aerodrome at an aerodrome with an ATCU that I would have received a "Land After" subject to the usual conditions, daylight etc.