See attached business card, I spoke this guy at the Classic Car Restoration show at the NEC earlier in the year. They come to you, so you either need your own facilities for accessing the underside of the car or somewhere locally you can hire a workshop with a lift for the day. They had a Morris Minor shell at the exhibition which had been half stripped of underseal, it didn’t seem to have damaged the paint underneath, loose rust had been removed but would still need to be treated. If you send them some pictures of the underside of your car they will give you an estimate. It’s an interesting process but having removed all the underseal I would want to epoxy and Raptor coat the underside, major rebuild territory, so it’s not for me at the moment.
I’m using a variety of Bilthamber products to treat rust, on the underside, Hydrate 80, followed by brush painting there two part epoxy, didn’t brush on well but that could be me so still experimenting! Also used Hamerite, again brushed on over Hydrate 80, much easier to apply but have yet to see how well that holds up. I would be interested to know what the costs are for Ice Blasting if you decide to make enquiries.
Regards Simon