immobiliser trouble

Hello all, I'm a newbie here and in a ton of trouble. I have a W reg freelander 1.8 petrol version and I can't open the central locking from the keyfob , or start the car. After having a new fob encoded it seemed to work ok for a while then the problem returned again. I have just had the car at the auto electrician and he has informed me that it's a problem with the central locking part of the immobiliser and if it is bypassed, it will render the tail gate redundant. What I would like to know is if anyone has knowledge of this type of problem, and can it be cured without resorting to a new unit which will cost in the region of £600+ by the time VAT and labour are added. Sorry to be such a pain in the ass and long winded, hope someone can help.
Thanks very much.

If I understand the system correctly you can get a replacement alarm control unit that can be coded into the system or buy a replacement s/h set of engine ECU and alarm unit together with its fobs, fit this and all should be well. But check first as I am more used to MGFs with the K series engine than the Freelander!

Not sure how bypassing the system causes a problem with the tailgate

Thanks very much Mantamad, it seems the offending part is called a body controller and is totally snafu. Apparently the tailgate is operated via a micro switch and some other stuff about signals I didn't understand. The autolec says there's more life in a tramps vest, so I'll have to try and locate another before the full price zero option rears its head. Thanks very much again.