We don't have pre- canned low level IFR routes in here so far as I know except for departure from major airports -eg. the "Juliet" departure from Luton and possibly heli routes within the London CTR/CTA.
There are definitely no IFR heli routes in the London area!
Radar units will sometimes be able to provide a radar service in Class G airspace (very often with limitations) but below MSA, terrain clearance is solely the pilot's responsibility and ATC will normally remind pilots of that fact.