This is a broad subject which I think breaks into three catagories.
Weather Radar
Two of the A&AEE Boscombe Down based fleet, TG500 and TG502, were both fitted with Ekco weather radar in nose mounted radomes.
A MET1 of 202 Sqn TG565 was fitted with Ekco weather radar in a nose radome for trials by A&AEE and was then returned to service with 202 Sqn, keeping it radome until retirement.
The RAE Farnborough, Meteorological Flight TG618 had a pod mounted under the nose, reported as housing weather radar although also said to be a sampling pod.
Bombing Radar Trainers
Eight T5's were produced by modification from C1 or MET1 aircraft by fitting H2s bombing radar.