RAF Shawbury is the main training base for all RAF, RN and Army helicopter crews. They've got (from memory) about 30 Junos. If you visit Shawbury on a working day it's not unusual to see 20 or so of them out on the ramp at any one time, and most will fly at least once a day. Their training course includes some night flying. You can work out when this is going to happen by looking at the airfield NOTAM's.
There are also 3 of the larger Jupiters which although based at RAF Valley are common visitors to Shawbury.
Since the Junos and Jupiters are a modern helicopter leased from the Airbus, they have all the modern transponders, so usually do show up on radar tracking sites. However, being helicopters they typically don't fly above 1000' and that restricts the range at which they can be detected, so whether they show or not depends more on where they're flying than anything else.
If you want more of a challenge look around RNAS Yeovilton or RAF Wattisham. Or the Hereford area