I'd phone your vet to find out as prices can change so much.
At my vet it's £15 for myxo and £10 for VHD, a good vet will do a general check up at the same time as the jab to make sure bun is healthy enough for it and doesn't have any other issues that need dealing with.
If you've got a simple question most vets and ask while you're there most vets won't charge you a consultation fee.