Would like to share my experience in case anyone might be in a similar situation. It was crucial for me to get my ILR 5 days earlier than 3 years and 11 months and I was pleasantly surprised that I managed to get that at Croydon office.
First hurdle was to get an appointment booked for this early date as when you phone them up they usually ask when your 4 year period elapses and do not book you for any date earlier than 4 weeks in advance of your relevant date. I was lucky on the third time as no questions were asked and I get an appointment for the date I wanted. My advice is to get an appointment booked as it saves a lot of time. You go in from a side entrance which is clearly signposted for those with appointments.
There was practically no waiting time at all until I got to a casework officer. Initial checks of the documents are done on the ground floor, no questions were asked, then a payment on the first floor by a credit card and finally you go to a caseworker on the second.
Once my documents were accepted I was asked to come back after two hours to collect passports and letters. It turned out to be another couple of hours before the documents were ready but you are allowed to go outside so you do not need to spend all the time inside waiting for your documents being processed.
I had a company letter supporting my early application and it did help to get it as the case worker did ask for a reason and checked the letter which confirmed my verbal explanation. Overall it was a very smooth and easy process so I even did not felt sorry for my £250
.Finally I would like to thank the board members for all advice and help I got from them on my way to ILR.
Big thank you and all the best to you all.
enpv