I imagine that one of our UK members will be along to suggest something but just in case I'll see if I can give you some hints. First the product not brand name would be contact adhesive or glue gun. I prefer contact adhesive myself but it can be pretty toxic smelling. Companies like 3m make the contact cement and I think they sell in the UK and Ireland. Another brand name that pops up when I Google is Bostick and they have contact adhesive. Contact adhesives come in both spray and can form like paint. Both can work but for joining foam I prefer the control of a liquid in a can. Sprays are good if you are gluing fabric to your foam or gluing large sheets together to make a block.
The second product, glue sticks, should be readily available in the UK and Ireland. Pretty much standard fair for craft stores. Low temp really works best and will give you less burns.
Keep a glass of water handy to dip your fingers in if get some glue on them. Also it can run and drip and makes spider webs. In fact just the other day I was gluing something kind of upside down and was not paying attention. Ended up with a glob on my bare leg (was wearing shorts) and it left a nice burn.
