Thank you everyone for your replies. Both links provided were the
items I was looking for. I didn't know they existed until I recently
saw someone walking out of Screwfix with a bag! I was being lazy and
thinking ready made ones would be faster to use but if I add in the
time to drive to the trade counter and back, then hand made is
probably quicker overall so I try and make some and if that fails, buy
some! Thanks again.

Stephen.