If your medical problem is still ongoing, then your paralegal has done the right thing in refusing the offer made, which in any case does seem somewhat low.
Your compensation is based on the actual injuries you sustained, which includes a payment for pain and suffering and loss of capacity, the injuries themsleves and any ongoing difficulties.
The independent medical examination will provide a more detailed prognosis which will also help determine the longer term problems which again will help determine the value of your claim.
On top of this, you will also be compensated for your out of pocket expenses, loss of earnings and any other costs incurred, so the offer of Â?1375 does seem to be very much on the low side.
The insurers will not be able to offer less, if yor paralegal is half decent (bearing in mind that they are not qualified solicitors) then they should be pushing for a figure closer to Â?4,000 - Â?5,000, possibly even more if it is determined by the medical expert that you may have this problem for some time to come.