Hi Martyd.
I use Dolmen as Ally says. This is my second year so no evidence of how a claim or breakdown would fare. However the scheme is covered by AXA who are a fairly reputable company.
The scheme is a special one for motorhomes, and as such you simply fill in the form and send a photocopy of your driving licence and cover note for your car insurance together with £250 and; bingo, you are covered.
Worth investigating.
Breakdown cover I get from RAC. The important thing is that My membership is through the Camping and Caravan club scheme called ARRIVAL. This removes restrictions on length and age of van which most companies impose ( including RAC ordinary membership) The other usefull thing that I have done is to take a family membership. So for about £240 last year my families four cars plus the motorhome are covered to the full range of cover available including european trips ( cars too). This equates to approx £50 per person, substantially cheaper than each person taking out an individual cover since basic membership is about £38. All members must reside at the same address though. Mine all do, for better or worse!!.
I have not had to call them for a european motorhome breakdown, but at least i have done the best I can.
A lot of people on motorhomefacts.com swear by the german firm ADAC who seem to do a very good europe wide cover. Worth looking.
All the best
Davy