Why would you buy from eBay, when you can pay the same (actually slightly less, it seems?) and get direct from the manufacturer, have much easier discussions should a warranty claim be needed, and be giving all the profit from the transaction to the company who has designed, built, and is taking all the risk of being in business, instead of some parasite sitting in his spare bedroom?
Actually, for those reasons, I'd be quite happy to pay slightly more!
Whilst ebay does still have some parasites selling from their spare bedroom, the link provided is to a company that has been trading since 1977.
Scottoiler's total price for v system, dual injector and bottle of spray comes to £114.90 (before discount) or £91.92 (after discount) excluding postage (couldn't find delivery costs on Scottoiler's website).
(Reputable) ebay price for the same = £82.89 including delivery.
I can see no issue with a warranty claim from the ebay retailer, even if you wanted to liaise directly with Scottoiler, as their registration section allows you to register a product bought from third party sellers.
Whilst with the discount arranged by bbb (thanks for taking the time to do that) does make them only 10% more expensive, without it, they would be nearly 40% (38.62) more expensive than a retailer (who is also taking a risk being in business).
Don't get me wrong, I have no issue with conciously paying more to one retailer than another if I can reasonably justify it (better service, supporting a local retailer, etc), but when a manufacturer is significantly more expensive than the retailers (who they've aready made a profit from), I find it harder to justify purchasing directly from them.