Are you looking at the Aerad Cranfield ILS Rwy 22 plate? Just looked it out and it has G in a circle at Henlow (glider site).
It also has the GP:
It has a strange procedure. You go outbound from the CIT (3.7nm from the thr.) then turn inbound and pick up the localiser. BUT, tou fly a non-precision vertical section from where you turn inbound until the CIT. You THEN fly a 3 degree GP from the CIT to DA. The plate has 2 'not below' check heights. The first is at the inbound turn of 2500 feet. The second is at the CIT of 1580 feet. HOWEVER, above this is written GP1580 indicating a check height for the ILS. Highly confusing!