The Woodhall Spa incident could be a 6lb Ground Bomb, missed during a cursory post war clearance. The bombs were filled at Forward Filling Depots where the mustard was stored in sunken lead lined pots. During de-commissioning all the pipework and pumping gear was dumped in the now empty pots, along with the odd left over ground bomb. During the 80s and 90s a 'final' clearance was undertaken, Riseley Wood cleared under op Coleman Keg, op Capsicum Jar was another at Escrick nr York. For the clearance the pots were clean bottomed, the lead lining folded down, back-filled and mounded over.
Tashengurt refers to the No 76 White Phosphorus Grenade, issued to the Home Guard to use against enemy tanks. Imagine a full milk bottle crate. Many were disposed of in the local pond, thus preventing ignition by exposure to air should the closure leak. No doubt there still are plenty around. PN, I don't think it would be WP bottles at Riseley, although a carboy of mustard was found in a hut during the clearance.