Compensation for transfer delay

cricketfanatic

At end of Oct, my IFA initiated an annuity purchase from Aviva with funds from two DC pensions.  Company A transferred the funds within 2 weeks,  company B took 6 months, with multiple (and sometimes duplicated questions on) forms to complete.  My quote obviously expired in this time frame, so Aviva went ahead with the pension from A, and did B's separately on a new quote. Over the 6 months it took to complete the transfer,  the annuity rate dropped, so my pension (for is c£400 a year less than the original quote/pension would have been.  I also missed out on up to 5 months' pension due to the delay in it starting. 

I complained to B, and after 10 weeks,  their response is to offer me £250 comp for inconvenience and c£1000 in interest for the delay in transfer of the funds.  They are only counting the period from Feb to April as a delay (in Feb they transferred the funds incorrectly,  they were rejected by Aviva, and it took until end April to do it properly). B seem to think that it's acceptable to take from end Oct to Feb to do a transfer,  and only seem to be admitting any error/delay on their part from the transfer error in Feb.

I think that I should be compensated for:
 - Missed monthly payments for x months due to delay in starting pension.
 - The reduced monthly  annuity for the rest of my life. I can  quantify the yearly loss based on the difference between the Oct quote v April. However, if I accept that it's reasonable for them to have taken a few months for the transfer,   I don't know what annuity rate I would have got in,say, Feb. As annuity rates were steadily tracking downwards, I can assume it was less than I eventually got. Also,  how do you quantify 'the rest of your life'? The Govt uses 20 years for the (now removed) LTA calc, even half of that would give my a lot more compensation than I've been offered.  I have a 5 year guarantee on the annuity, so that's a definite, but am not mentioning that until we reach a stalemate.
- Interest on the delay to my receiving my lump sum. 
 - An increase in the £250 inconvenience comp,  as  I made many calls over the months to try to speed things up.

All of the above were stated in my original complaint, but have been ignored. I'm going to call the complaints officer to state my case again, but wanted to sense check the above.

 Is it unreasonable of me to assume that if company A did the transfer that B should also do it within the 30 day quote period - or at least within a couple of months? 
Is claiming for lost future pension unreasonable,  or is that just consequential loss? Even if we agreed a date on which it was reasonable for them to have completed the transfer, say 2 months, I don't have an actual annuity rate for my particular case from that date.  
What interest rate should they use? They've used Base Rate + 1%, but I think the FS Ombudsman use 8%?

I'm prepared to go to the Ombudsman if I don't get a substantially increased offer.  Does anyone know whether,  if the Ombudsman don't agree with me, will I still be entitled to the original offer (as they've already admitted some wrong doing)?
And views appreciated, as I really don't know how hard to push this. 
Thanks in advance for any (helpful!) comments, and sorry for the long read!