Correct, HLV in green in Mayners
This is the photo I had in mind (thanks, Ernie) but BOTH are luggage vans, one in silver and one in green. Luggage vans ('hooded vans') has a central pair of door whereas the HLV had TWO pairs of doors fore and aft of the centrally located boiler with exhaust vents on the roof of the HLV. This is best seen in Ernie's second photo where the third van from the loco on right is a HLV in green (double doors, exhaust barely visible because of the angle) followed by the silver LV next to the BnT. I believe the HLV still had capacity for 3T of luggage and were probably used year round even when heating was not required and can be seen in many photos taken in June/July. However as you say, may have to be taken in for maintenance before the autumn again.