Hi
You are not the only one they are holding passports for longer periods. This unusual practise started in August 2014, this could be for a variety of reasons particularly LVO had issued MR and PPR in great numbers and cleared cases in ultra high speed which has resulted in visa-stamping delays. Its been 50 days for me still no sign of passport and if you search the thread you will find people who had to wait for like 85 days. Anyway this is my opinion, there is only 1 strange case in which passport has been submitted and after 60 days while answering to applicant enquiry VO informs that your file is currently awaiting BG checks we will proceed once received. I thought they issue MR only after BG checks are cleared, hence LVO like is said here is unpredictable!!
And yes I have also send 3 enquiries to LVO and they have not responded to any of them.
The only hope I have is I'm NOT the only one stuck at this last stage there are quite a lot of us, therefore I would like to welcome you to the waiting club
What does your ECAS show? if it shows 'DM' then you will receive your pp very soon because this means that your visa has been issued and is awaiting delivery
Kindest Regard