Please Could I have your opinion.......

I wonder if anyone could give me any advise please:

I have claimed IB for a number of years. Last December I got an IB50 form to renew my claim. I took a while to fill it out, and just before i finished, and also got some supporting info from my 2 specialists, i became more ill and was bedridden for a while. Jobcentre plus in Plymouth gave me until march 17 this year, to get my form back. By this time I had it all completed and letters from my 2 specialists were enclosed. Having been a member on here for several years I realise how important it is to do these things properly!
I sent it back by recorded delivery and they recieved it before the deadline. I have waited and waited for the outcome of this but haven't heard anything. Obviously its now june but I know just how slow they are sometimes.

Anyway today a letter came out the blue, not about my existing claim but telling be to expect a phone call about the migration to esa. They said they will shortly be sending me ESA50 etc etc. Not the best post I've ever got!

Can I be expected to have to start completing a new claim before I know the result of the prior one? I realise IB is being phased out, but at the time of my renewal it was the "live" benefit.

The result of the original claim surely makes a difference to my migration date, so do you think I can insist of having that dealt with first?

Or can they just do what they like?

Please let me know your thoughts. good, bad or anything I could try?
Thanks MIK

Thanks Gordon.
Thats a good point.
I've been pretty fed up all day, and i've been trying to come up with a good reason why to review someone before the've heard back from the last review, isn't fair?
I'm wondering if i should phone up to try to get the result of my IB review?