eBay's position on warranties / guarantees that sellers offer is clear.  They cannot offer any further protection against items not as described outside their 30 day MBG Money Back Guarantee policy.  They do not physically see the items being sold so cannot guarantee their working correctly for 5 years.

If this was purchased from a Private sellers,  warranties are usually not transferable and belong to the first purchaser.

If you purchased from a UK business who offered this warranty and is now not honouring it,  then it is worth contacting Citizens Advice for any further steps you can take.

As for going to Court,  forget that move, you'd lose a lot of money!

@gost577