I asked my local garage for their TPS account no. and I’ve been using it ever since.
Maybe worth asking a local garage around you for theirs. Or get a garage to order parts if they won’t give you their acc no.
TPS account discount is dependant on how much you buy month on month - this suggestion is not that daft as it adds to the garages sales figure.
I have been using my local TPS for years. They have even given me an account number to use, not that I plan to make a habit, but I can still actually ruck up without calling in the order before.
For service stuff I buy Quantum Platinum oil by the cube, works out (iirc) around £26 for 20L from TPS
Edit: Forgot to mention one anomaly with TPS is they can't sell special tools, that is dealer only and then its their discretion.