Cornwall boast a large range of tourist accommodation, ranging from 5 star luxury hotels to B&Bs, guest houses and hostels. There is also a large number of serviced holiday cottages that can be rented from anything from a long weekend to upwards of a month.
There are Tourist Information Centres TICs in most major towns. Theses are normally run by the local council and can check latest availability on the day to save having to phone round a number of B&Bs and guest houses. Note that they are unbiased and won't express an opinion on accommodations, more than giving its tourist board rating and facilities.
