Jewellers to melt down ring?

It definitely can be done, although probably not at a high street jewellers like H Samuel. Your best bet is to go into an independent jewellers (the sort of place that makes their own jewellery), show them the ring and ask them about it. If you're anywhere near Birmingham, the Jewellery Quarter is full of places that can do this. They will have to send it away, and it may take a few weeks or so, but it can definitely be done.

Harvey's jewellers in Wakefield offer this service. (Don't confuse them with another company of a similar name!)

You can take the ring there, along with any other old gold and have it melted and made into a new ring.

I know Phillip Stoner in Manchester will do it, they offer a design service as well