Where in Canada are you from? My husband and I moved to Leeds from Ottawa in Jan. I am doing an M.Sc. here and he is teaching.
Ok, I'm not sure the housing differences between Leeds and Devon but as someone else mentioned rightmove.co.uk is great, I used them to find our flat. Going through a reputible site like that is important because as you've found, there are a lot of fake ads out there.
Banking here is a bit of a mess. Get into a back straight away and set up an account. It takes a week to get your debit card (they mail it to you) and they mail your PIN seperately (which you are assigned). I think you can change it once you get it if you like. You can get an account for free at most banks. We are with Lloyds, they seem pretty good so far. Started with HSBC thinking because they are international we could move things between here and my Canadian account but nope, all seperate!
Things in England cost the same as in Canada except they are in pounds so it is generally more expensive by maybe 30%. a nice thing is that the tax is already included in the price so no extras when you get to the cash, but they pay 17% tax and it is rising to 20% soon. Clothing and shoes are quite cheap here. What ends up being a little pricey is heating costs as many places seem to have electric heating and they pretty much have no insulation here. Just wait until it snows. 1 cm of the white stuff and the whole country grinds to a hault. Luckily it rarely snows. 
Phones are cheap but you will not be able to get a good deal on a plan unless you have something with your address on it (e.g. a utility or council tax bill) so you may have to do pay as you go at first, which is fairly cheap anyhow so not really a big deal. It took us a month before they'd give me a good plan and nice free phone because I have no credit history here. Even though back home i own my house and have excellent credit.
What else, oh, if you want a tv you need to pay a yearly tv license which is around 140 pounds i believe. this it just to own a tv, is not for programming or anything but its required. we just ended up watching shows on our computer. as long as you don't watch live tv online its legal.
Also, budget for council tax. depending on how expensive your flat is you will be required to pay some amount of this tax, its pretty much like property taxes back home. so ask your landlord what it will approximately be, they should know this.
Don't stress too much about not having a place yet. Lots of places don't rent as far ahead as in Canada. and many places will advertize a weekly rate, the monthly rate will be a little more than 4x the weekly rate (because its based on 52 weeks a year).
Any other questions please feel free to email me: ruby_tuesday44@hotmail.com
Jaimee