Over the last 3 or 4 years I've become a fan of Cerafix Grabs Like Nails. It is now off the shelves at B&Q.
Its replacement at B&Q is B&Q Exterior Grab Adhesive, which IMHE after trialling it, isn't a patch on Grabs.
Puzzled enquiries yielded:
Cerafix is a B&Q own label brand, as was Grabs Like Nails.
Maker of Grabs was Henkel which still makes several other Cerafix products for B&Q. B&Q wanted to pay a lower price to Henkel for Grabs. Henkel w/couldn't play ball, so B&Q chose a lower spec from xyz plc.
Henkel suggest their Unibond Megagrip adhesive as substitute for Grabs. Stated availability is builders merchants such as Jewsons, Travis Perkins.