Medical certificate for >180 days absence ILR

[SPILR]

Hi, I have situation wherein I wont be able to split my 'more than 180 days' absence from the UK into two 12-month periods at the time of my ILR application. The absence was due to sickness (of 51 days) during my planned annual vacation to India in 2014. For this sickness period I have a hand written medical certificate (from 2 years back) from my Doctor, General Physician (from India) on his letterhead which is stamped, dated and signed by him.

Apart from this certificate, I don't have any other documents such as hospital bills, medicine purchase invoice etc. as I never went or needed to go to a hospital then. I do have the original flight tickets (booked to fly back to the UK) which I had to cancel due to the illness. I recently consulted a lawyer in London who seemed to suggest I cannot have a handwritten note as a medical certificate as part of my supporting document for my ILR application, even though this is stamped and signed by the doctor on his professional letterhead. Could anyone please advise whether it is true that UKVI generally don't accept such medical certificates if they are handwritten, even if its on a letterhead, stamped and signed by the doctor? Does this make my case weaker?

Specially in case where the document is for supporting a more than 180 days absence from the UK? Any advise would be much appreciated. Thanks.