Hello Chris the Brit. I know mostly about Cha-am lovely place, about 25/Km North of Hue Hin. Plenty of Brits live there mostly older men retired. Also Aussies, Yanks and Southern Folk, Danes, and lots from all over Europe Some with wives and family others well. Lots of small bars, restaurants, massage places and yes girls mostly to help Farangs...TIT
Hue Hin housing rentals costs are about the same as Cha-am. Hue Hin is a much bigger town with big shopping centres and traffic which is a dogs dinner to go with it, it rivals Pattaya but on the West Coast of The Gulf of Thailand. Cha-am traffic is only a dogs dinner at weekends as thousands of BKK's people descend on the place and stay a few nights Just lovely during the week, weekend still OK don't ride your m/bike though. Hue Hin has (may I say it) a bigger red light area compared to Cha-am. Yes bigger everything and a few Farang ratbags?
  I have quite a few friends who rent 2 story town houses 2BR upstairs + bathroom. Down stairs which have outside front court area big enough for a bit of under cover BBQ area and enough room to park a car and perhaps 2 motorbikes or push bikes. Quite a lot of units like this available in Cha-am about 1 km or more from the beach mostly quite cheap, can be cheaper if a bit run down. This layout is very common in all Thailand.
These places have quite a large main living area downstairs of about 45 sq/metres and a nice separate fairly large typical good Thai kitchen inside + downstairs bathroom. No back door (normal). When you rent one of these town house apart from sheets and towels a TV, air cond. fridge, stove, tables and chairs, inside lounge and quite a few other pieces of furniture are included in the price of rental. (not fancy but cheap) I expect to rent similar for my next stay in Cha-am and pay Bht 8500 P/M for 12 months rental. It would be 25% dearer P/M if you took it for 3 months only. Often the means of working out the discount for 12 months is they charge perhaps 12 months rent of Bht 11500 and you get the 11th and 12 month rent free. But get it all in writing. Can come back to bight you.
I have looked at several of these, there seems to be quite a lot of others like these available to rent in Cha-am, probably a bit expensive for Thais. When I return soon I will be looking to pay Bht 8500 P/M + elect and water for 12 months.
 You could also rent something a bit bigger 3BR in a gated community with security guards round the clock for about Bht 15000 p/m or more. Some better facilities like communal swimming pool etc.etc. This may be 1 to 3 KM from the beach, very nice and clean.
I'm not sure of the population of Cha-am but 35,000 might seems about right. 70,000 at weekends (sometimes). The beach extends for 6/7 KM, apart from 2 small police stations it has no building on the beach side all. At weekend when all the visitors arrive cars park anywhere with the assistance of self appointed beach chair traffic directors and often gridlock the place (sort of works) but again TIT.  Much better then Hue Hin Beach where much of the residences are built right up to the beach and sometimes over the sea, no road running along to the beach. Parking at weekend there is a catastrophic dog's dinner. Most days it can take 25 min to drive the 6/7 km down the main road through the town...not for me.
Hope his helps...regard DavoWaldo Esq.