In reply to PPP:
I've come across them before but never bought from them - you do know they are a small newish business? They are not vat registered (taxable turnover of less than £79000) so will be cheaper. If you are suspicious purely on price then bear that in mind.
Does it feel right to you otherwise? Do you trust them with your details? Are you able to use S75 protection?
Remember all businesses have to start somewhere, but if you are not prepared to risk it, then walk away.