Both will do it, if you are a member it is slightly cheaper. I think there is premium if it is a camper conversion as I guess it makes the job more time consuming.
Not 100% what they check now but I had some used cars done with the AA and the guys were very thorough giving you a follow up phone call and written report. I think it cost about £250, could be more now, but if you are spending £10k or so it gives you that extra piece of mind. Just hope you dont have to do it on more than one vehicle! I: