How to chase up AP1/TP1?

I submitted AP1/TP1 5-6 months ago and have heard nothing except for the autoresponder with a reference number for the application. Heard nothing at all since. Is there an approved way to chase it up and ask what's taking so long?
The email we received said it was estimated to be done in January.
Thanks

Martin - once submitted such applications might wait a long time before being processed. There's rarely a need to 'chase' as the application/transfer is protected once received by us.
If an urgency should arise, such as a linked/dependent transaction then a request to expedite can be made - Request an expedite - GOV.UK
If there's no urgency then it's a case of waiting until we contact you when processing starts/is completed

Thank you for the reply. 
The evidence required sounds onerous but that aside, do you have any idea how long it will take? I do'nt understand why they would respond to say 'expected to be done in January' and yet in March i have no recourse or way to even ask why it's still not done, and when it might be. 
Are you able to take a guess on how far behind they are (clearly they are behind since they produced the January estimate when it was submitted)

Martin - average timescales for a TP1 are around 14+ months at present and have been for a while now.
If there's no urgency as per the expedite criteria then there's no recourse needed. The application and change of ownership are protected and how long they may then wait very rarely has any impact other than a degree of uncertainty around timescales as you have expressed
If you have the provisional title number I can offer a rough estimate in terms of a date?

Oh, I thought this was just a support forum for advice on how to submit applications. I didn't know you could check things, that's useful and kind of you thanks. I will find the provisional number. 

PS "average timescales for a TP1 are around 14+ months at present and have been for a while now" - If that's the case, why did they provide an estimate of January? I am confused. If nothing else it led to unreasonable expectations! 

I will reply again when home later. Thanks