Selling property in Sri Lanka as a foreigner with existing leasehold

Hello friends,
I'm new to this site but picked up on a forum regarding the purchase of land in Sri Lanka by foreigners and was very impressed by everyone's input and replies. Really hoping to get some answers to my queries and most grateful to anyone who has time to reply.

I bought some land in Tangalle Sri Lanka about 12 years ago as a 99 year leasehold and put the freehold into a local friends name. Sadly however a few years later he died and so the freehold has passed to his wife and children who do not speak any English. I am now in a position where I need to sell the land and the family are also willing to sell the freehold, for a cash return of course. I need to know what sort of percentage would be usual for the freeholder to expect in this situation, they did not invest any money in the first instance. Also, I would like to get the land professionally valued and seek advice on reputable real estate companies, legal and possibly financial advice regarding taxes due from sale of land. There is a lot of information online regarding purchasing for foreigners in Sri Lanka but I can find little advice regarding selling.
I will be travelling to Colombo at the end of April to initiate the sale so hope to be able to find the right professionals before I arrive.
Many thanks in advance