The 0371 521 33 00 number is local call rate.
That don't provide an email address as such, but if you log in to your ebuyer account they have an Enote facility whereby one can correspond with them (and it does work as I've used it on a few occasions).
Alternatively, you could try their technical support team on 0330 3 339 390, but you may find that they will want an RMA (returns) number before talking to you.
Like a number of vendors they sell extended warranties and may argue that if you wanted a warranty to run beyond the "standard" 12 months then you could have purchased an extended warranty. But that does not mean that you do not have rights (e.g. in that the product should be expected to last for a reasonable lifespan).