Whilst looking for the solution to the problem of the remote entry failing to work unless right up against the windscreen, it seems like the only solution provided was to change the receiver module that sits up on the drivers side windscreen pillar. I have found that this is not necessary....

remove the cover from the receiver ... on the top right hand corner is an adjustable potentiometer, recognisable by the cross shaped screwdriver slot. It appears that this is affected by both heat and/or moisture ( humidity ) and can sometimes act up. My answer to the problem is to rotate this potentiometer a few times, pressing in lightly while turning, then reset to the best possible position by trial and error by pressing the remote and moving further away each time till the optimum position is found. Actually this does not require that you leave the interior of the car. Replace the cover of the receiver. Job Done.

If this fails .. try a little squirt of WD40 on the potentiometer and repeat the above process.

If this fails then I guess it's back to the dealer for a new one like everyone else has said