Adverse possession after contact with owner

Hi, I was just looking for some advice on adverse possession after owner of land has been found and contacted please.
in the course of selling our house, it was found by our buyer that the small piece of land for our back garden actually belonged to a company that owned the land/houses behind. We had been totally unaware of this and thought for all intents and purposes it was just part of our title deed-our solicitors when we first purchased the property 8 years ago never mentioned anything either. We have since found a document from previous owner in 2008 who found this company owned the back but never said anything to us or solicitors etc. Since finding this out our solicitor dealing with selling our house reached out to the company who want a valuation done on the land and all fees paid to then buy it off them etc. Since at least 2002 our back garden has been fenced in, used solely and exclusively by us and the previous owners with no challenge or complaints or anything and has a curb built round it and peoples drives and a road bordering it. We found out we could apply for adverse possession but our solicitor was unsure if this would still be possible because she has reached out to the company to enquire about it? This led us to wondering if after them getting a valuation quote for the land (which they are requesting we pay for) we would still be able to take adverse possession of the land? We had all paperwork ready to go to apply and also to expedite as we have a buyer and our new house depending on this land being sorted, but now unsure best way to proceed and so wanted to check if still possible to proceed with adverse if owner has been contacted? Any help at all would be much appreciated as this has just been a nightmare! 
thank you 
 

Hi Olivia - our PG 5 offers guidance on how to apply for adverse possession and the 'essentials' involved. You do need to rely on your legal advice here as to whether your claim is legally valid and how to then apply as appropriate
Practice guide 5: adverse possession of (1) unregistered land and (2) registered land where a right to be registered was acquired before 13 October 2003 - GOV.UK 
We don't offer any wider guidance as it's important to confirm the legal requirements have been met before you apply. We won't consider if you have them met both the legal and registration requirements until an application is actually submitted