Beware of using a cottage letting company called ST Ives Cottages or Coastal Cottages (the same company - www.stivescottages.co.uk).We rented a cottage through them called Fishermans cottage. although it was a nice cottage it cost £660 for one week. We spoke to the people in a similar cottage next door who had only paid £230!
On complaining to St Ives cottages/coastal cottages they were not interested as they had our money via online booking and they did not think the price was a rip off, even though it was proven that they had overcharged us to the tune of 3 times the price of comparison properties. The price for the same week the following year was less as they had charged us for easter bank holiday weekend by mistake - but they would not admit the mistake or refund any money.
I did a lot of research and found out I could have rented one of the top properties in St Ives for what we paid for a 2 bed cottage. I complained to the local hotels association and kept writing to the owners but they kept defending themselves saying their cottage was better than all the others. beware of parting with large sums of money based on a few pictures until you have researched comparable properties!
It turned out the owners were not local people and just interested in getting as much money as they could get away with. The cottage was nice, but not 3 times as nice or worth three times the price of the one next door.
My advice is to go through a reputable letting agent - Lanhams in the town has dozens of cottages to let at reasonable prices - their website can be found at stivesholidays.com. St Ives is a lovely place and there are lots of great places to rent - try Lanhams they should have what you want and they are a reputable agency (www.stivesholidays.com)