UKC

Previous owner put a border strip along the walls of a room. The adhesive must have been very strong - not wallpaper paste. Struggling to remove. Even white spirit and pan scrub is struggling. 
Any ideas on a suitable solvent or other method?

PVA?
Time to get the steamer out.

No, stronger. It’s dark - like an evo stick. I’ve just tried sanding it - that works. 

Seriously, try a steamer. Most glues these days are effectively a plastic, works great on tile glue and that seemed impossible until I gave it a go.  It softens the glue and allows youto lift it with a scraper.

You need one of these.  Razor blade sharp and as someone else said steam.

https://www.toolstation.com/prep-heavy-duty-scraper/p29412

It's probably contact adhesive, if so a scraper is probably best.

Panel wipe removes evostick. A car painter would be the best source of a small amount. 

Jk

Thanks guys - lots of methods to try out. 

Depends.

If it's a polyurethane then you can't dissolve it but you can soften it. However other than acetone (nail varnish remover) the chemicals aren't something you'd find in B&Q.

https://www.quora.com/What-is-the-solvent-of-polyurethane-glue-fevicol

Polyurethane is the base for the gorilla glue the woman used for hairspray.

https://www.buzzfeednews.com/article/adeonibada/tessica-brown-gorilla-glue-tiktok-surgery

It's unlikely the glue is epoxy but if it is, paint stripper will dissolve it.

One thing that might work is just using a heat gun to soften it before scraping it off.

Pretty sure foam gun cleaner is sold in B&Q (under the screwfix no-nonsense brand), it's certainly available in Screwfix. That'll soften cured polyurethane so it can be peeled or scraped easily. 

Heat works to soften most commonly available glues.

jk