Polyurethane glue is for woodworkers, primarily.

It is (in the Colonies) about five times as expensive as ordinary wood glue (Titebond original formula, for example) and offers no real performance advantage to modelers over wood glues.

In some situations polyurethane glues are counter-productive, as in the case of sheeting foam cores with balsa skins : as the glue expands it can force the skins away from the cores resulting in the classic 'starved horse' appearance (washboard). That's probably the major down-side to PU glues - the expansion tends to push the wood bits apart causing if nothing else misalignment of the wood bits.

The only instance where PU glues shine over aliphatic resins (wood glues) is where there is a need to fill gaps, which of course normally result from poorly fitted wood bits anyway.

Check the Titebond or Gorilla Glue web sites - they likely have UK distribution.