Moffat 3500 Thermoset Hob Gas Leak?

We have been advised that my mum's Moffat 3500 hob has a gas leak, probably due to broken valves. The gas supply has been turned off for the time being. I am wondering if this is something fixable or if I'm going to have to get another hob. From another (very useful) post and response here about this type of hob, it seems it's larger than a typical one - it certainly looks that way, like a modern 5-6 burner hob maybe - and is about 25 yrs old. It is fitted into a kitchen work top over a cupboard. Thanks very much for any advice.