Property Problems Solved

Hello: We recently bought a shared ownership property in dec 08 it is as it says on the advert a first floor 2 bed couch hosue style flat over a garage and allocated parking. it was always made known to us we owned a parking space AND the garage. The garage is exclusive access from our hallway by a door. The mains fuse and pipes are all in the garage for our property. On the estate agents advert it says garage and allocated parking. On the lease it says garage but does not mention a parking space however on the land registry it shows we own a space in the parking lot. recently the government company we part own the property with has told us we do not own te garage and there was some mix up with the building and someone down the road is missing a space and/or garage and that our house was not valued as having a garage included in the price. They have wrote to us saying they have sought legal advice and can offer us a Variation of Deed so that we have "exclusive rights to the garage" IF we give up our parking space.; I contacted the solicitor we had used during the buying who thought we owned both garage and space. I am now really confused what to do. The mortgage company has our deeds so should i request a copy? I obviously don't want to give up the garage or space and do not want to be intimidate by these people into signing anything. Surely the soilicitor who did the buying and completiong for us would have seen every documentation and questioned what we owned during the buying process? Who is at fault here? Thanks