Hi Diane (I'm presuming thats your name)
I think joining the ICB is worth it. Its not too expensive to be a member and the practice licence fee includes your MLR which presumably you currently have either with AAT or with HMRC.
I dont know what the costs are to transfer to ICB but hopefully someone from ICB will let you know. Otherwise if you have to retake exams through ICB then if you plan on going through distance learning I strongly suggest Ideal Schools. WWW.Idealschools.co.uk Not only are they very responsive but have a couple of closed Facebook groups which are very supportive.