They are all the same. What I get annoyed with eurocar parts is their discount 50% everything online when I try it that item is excluded from the offer. Halfords is another one bought a fold up bike for the boat reserved online paid in store. In stock in the store. The same man in store put it together. I saved £150 doing it online rather in store.
I dont think I have ever managed better than one random 10% discount at GSF because "I must be a member of a VW club" offered by one sales assistant. I have always managed to buy stuff that is either not discounted during an offer, or I get an email telling me about the discount about three days after buying it at full price.
There used to be Regulations on sales - it had to be at a higher price for X number of days before it could said to be a sale but it seems from a quick Google trawl, that may no longer be the case - difficult to enforce I suspect, especially with a reduced number of Trading Standards officers. Glad you helped the old guy, it was a good thing to do for him - it seems you have to prepare yourself against being ripped off at every turn at the moment.
How much for wiper blades????? Ouch. I just bought some Aero style for the wife's Hyundai i20 for £6, even the Bosch ones were only £24. I think for the old style wiper blades I would buy replacment rubbers instead of the whole mechanism.