Elstree could sell the aircraft if the parking is not being paid. Their terms and conditions will have some period within them after which a lien on an aircraft could be enacted.
It takes a coupe of registered letters with specific notice periods and then they could auction it - or possibly sell it by private treaty - if they can prove they have achieved the best price.
The big question is why you would want to buy it. A lycoming engine left for how many years - full rebuild necessary? An airframe used in salt water and then left? An airframe which is essentially full of hydraulics and a UK GA maintenance regime which is a licence for extortion.
Buying a certified aircraft for restoration is a huge gamble. If you could find a maintenance company that knew their way around Lakes (whilst there are a couple of Lakes registered in the UK, the one guy I knew who had one hated all the maintenance organisations he visited with a vengence due to their ignorance......).
On the other hand there are a couple fo sale in flying condition in Europe - what is the sensible thing to do?