Most trial/surveillance drops were against the Hard Target at West Freugh, which, supposedly, was laid to WP spec. Only SG357 munitions were dropped and the dispenser retained on the ac.
AFAIK no HB876 mines were dropped at West Freugh, the range not being suitable for such munitions; trials and surveillance of the 876 were conducted on Eglin ranges.
The SG357 was very effective on the target, creating a camouflet and heave around the edge. Clearance of ux SG357s either complete or ux secondaries was a long and complicated job, involving an RC Hymac in 3 roles - concrete breaking, excavating and 'grabbing'; two RC EOD wheelbarrows and an RC sawbench.
In late '91 I was involved in a UN visit to Iraqi airbase H2, I was not able to get to the runways to see any results of JP233 - that was not my brief, but the airfield was rendered unusable by bombing: HAS doors blown off their hinges and the 'contents' a plie of molten metal, even the gym took a hit. There were ux cluster bomblets still laying in the gutters. One thing that struck me was the preparedness, not that it did much good, air raid shelters were plentiful and well stocked with food and medical supplies, in stark contrast to those in the UK and RAFG.