Oops i was looking at 126
Yes 216 is the SAS base at Credenhill.
As there is no service there and it is H24 the best advise is to speak to London Information on 124.75 when going to your destination.
You cant miss the zone. Look for a load of huge satellite dishes which is actualy D147, north of those is a load of big green sheds that is D216 and to the east of that is Hereford town