Firstly, I need to say I have never tried the Toolstation glue, so what follows is on that basis.
I have used Titebond III for years for both model and full size construction. I have some furniture pieces which are much older than any of my models and show no signs at all of glue failure. Great glue! That said, I have occasionally used other glues of uncertain parentage and found them to be perfectly fine. A point to bear in mind is that few joints in a model boat carry the sort of strain that full size joints do, and all these glues are designed for full scale use.
As for shelf life, I suspect this is a very conservative estimate to ensure they aren't caught out. I have a bottle of Evo Stik white glue that has been knocking around for donkey's years and it still does the job (once I clear the nozzle!). So in your position I would be happy to go for the Toolstation glue.
Greg