Do you know for absolute certain that the bottle itself is leaking? I've got a Skoda Octavia which had a leak which appeared to be coming from the washer bottle, but it was in fact the pump leaking. The internal seal was worn and was dripping very slowly from the weep hole. Are the windscreen washers as powerful as they used to be? If they aren't it could be another sign of a leaking pump. Because of it's location it was very difficult to see exactly where it was leaking from until I removed the pump and could see a water trail. I replaced the pump and I've not had a problem since.

The pump slots into the bottle through a rubber grommit type seal. It will just pull out and push in. Nice and easy.....

you sure your rear wiper pipe hasnt just come off gedi?dont know about your 1.4 but my 1.9 has a wee connector behind the bottle that you can not see unless taking the bottle out,, you do know they have separate pipes from the front washer?? and if the waters not coming out the rear then thats surely where the fault lies especially if you can see water leaking,,if the problem was with your pump or the bottle itself then it would obviously do it when you were using the front as well,,,and from what you have said its not leaking when you use the front??take the bottle out and check all the pipes carefully,,even though a garage has checked dont mean it is ok,,sorry to say but some garages cant be bothered with wee jobs like that and just want you on your way asap,,as well as being a nightmare to find the leak sometimes,,if its a split pipe then the hole could be as small as a pinhead,,,take the bottle out its only held in by 2 plastic screws if its the same as mine and double check it,if the connector is still intact then hold the bottle up and get someone to squirt the washer for you and look for the leak