Thanks for your enquiries.
It is normal for a Buyers Solicitor to request the Seller's Solicitor to discharge any service charge or ground rent arrears on or before completion (as legally, their client will be responsible for any such arrears post completion).
Therefore, when the Buyers Solicitor receives a copy of the completed LPE form from you, via the Sellers Solicitors,the arrears will be picked up.
However, if you want to be cast iron, I suggest that when you answer the relevant questions on the LPE Form, you also put the following "Please note all arrears of ground rent/service charge need to be cleared before we can deal with receipting any Notice of Transfer".
(This will make the Buyers Solicitor insist that the Seller or his Solicitor clears the arrears on or before completion)
This should certainly do the trick!
I hope this helps, and f so, I would be grateful if you could rate my answer.
If you require any further clarification, please let me know.