http://www.caa.co.uk/docs/33/CAP168.PDFSee above...
All airfields... and a heli-pad is classed as an airfield, have to have the appropriate category fire fighting cover according to CAA rules. The minimum is cat 1 which will be trained occasional fire fighters with hand held fire fighting appliances, usually found at grass strips, up to Cat 10 like Heathrow.
Aerodrome Category
(RFF)
Aeroplane Overall Length
Maximum Fuselage
Width
Special up to but not including 9m 2m
1 up to but not including 9m 2m
2 9m up to but not including 12m 2m
3 12m up to but not including 18m 3m
4 18m up to but not including 24m 4m
5 24m up to but not including 28m 4m
6 28m up to but not including 39m 5m
7 39m up to but not including 49m 5m
8 49m up to but not including 61m 7m
9 61m up to but not including 76m 7m
10 76m up to but not including 90m 8m