Whoops, I sent a private message to the site owners before I realised I could post a suggestion in here too! My current vet is good with guinea pigs (and a lot of other small or exotic animals - they even have an axolotl on their books apparently!) Based on the Wirral, in Merseyside - so good for anyone in/around Liverpool, Wirral, and parts of Cheshire (I note there's a few vets already in Cheshire listed).
It's Hoylake Veterinary Surgery, 43 Birkenhead Road, Meols, CH47 5AF, phone number is 0151 632 5676. The vets I see there who are pig-savvy are Rob and Maria. There's a website if you google Hoylake vets and need any more info, and they've got an out of hours service too. I found them after my last vet wasn't experienced enough with one of my old pigs, resulting in him passing away - these ones have so far dealt with an unexpected pregnancy, the check up of the babies, a nail clipping injury, and two separate abscesses over the last couple of years for me. They're always very friendly and helpful, have the time to answer any questions, and most importantly seem to have the knowledge and experience I was looking for in a new vet!