It isn't true that you had no warranty, what RT clearly says is that the extended warranty doesn't apply on framesets, I'd never assumed it did.
For everything purchased in the UK, and the EU, there's a minimum requirement - Any fault appearing in the first six months is considered to have been there from the start. A fault appearing after that, is covered for a reasonable time up to 6 years, depending on the goods, their use and expectation.. It's debatable how long that reasonable time should be on a cycle frameset, but it's usually accepted that any consumer goods not considered disposable should be covered for a minimum of two years.
All warranties rely on a fair amount of goodwill. If the fault is disputed, it's the retailers responsibility to prove it was caused by the consumer if it occurs in the first six months. Any time after that, whether the warranty is statutory or contractual, the position is reversed, it's the consumers responsibility to demonstrate either the fault was there from the outset, or is the result of faulty materials or workmanship. Good luck to anyone who thinks they can do that!
Basically, after six months, unless you have something that formed part of the sales agreement that says otherwise (like unconditional) you're suggesting to the retailer that the fault shouldn't have occurred and hoping they agree with you.