Chevvron - I don't have the document at home but I can imagine it goes along the lines of
"radar may be used by the controller to identify an A/C for his own purposes... this identification does not infer that a radar service is being provided" (dragged out of the back of my brain - it's a couple of years since I did LARS)
... You do not need a radar to provide a full FIS... and I am with Bern Oulli - I doubt if there is such a thing as a limited FIS in the book(leavesden notwithstanding),
Surely your example was more a way for Leavesden to inform people that they might not get afforded even the 'full' attention that FIS normally gets(??) - i.e. an alerting and information service - nothing to do with radar, more to do with nav warnings, warning a/c that are believed to be in the relevant area of any major air activity that is known to the 'controller' etc etc and also liaising with radar units/D&D as part of an alerting service
Widger -
There is nothing wrong per se with the limitation of a service - it is very valid when operating near the theoretical base of radar or in areas of known clutter etc - it should not be used as a get out for giving a gash service, but it should be used for as it is intended... to inform pilots that some intruder that in one direction (from below/the west etc etc) radar coverage is not ideal to guarantee that an ATCO will see all traffic.. it helps a pilot who will then spend a bit more time with the mark one eyeball in those areas.
I would go in totally the opposite tangent from you in this matter - I would say that an ATCO was negligent if he omitted to tell a pilot that the radar service he/she was getting may be degraded in some way!