Cost of Living in Galle (Colombo)

Good day all
I work for a company that is based in London, but has an operational base in Galle Sri Lanka.

We believe we are being quoted an extortionate amount for a 6 bedroom villa plus all mod cons.

We intend to have a 6 month contract and we are looking at what the actual cost (realistic) costs of a 5 bed villa in Galle with a cleaner, day and night watchman etc would be.

if anyone can give me an idea what the average cost of the below is i would be most grateful:
5 bed villa in Galle
Cleaners / per day
day/nigh watchman / day
utilities / month
any other factors we need to be aware of.

thank you so much for your kind assistance.

ps i've posted this on the 'housing' forum as well as not sure which would have been the quickest to get responses for. Sorry ... first time user! :-)