Firstly, I'm not sure property prices are going to rise much in the UK in the next 6 months, in fact, in most areas they're likely to be stagnant or slip back.
Renting a property whilst looking round for a place to buy is a reasonable idea. It might be worth telling the prospective landlord or agent your situation and only signing up for an initial 3 month contract if you can (there's no reason for a tenancy agreement to be 6 months though most landlords prefer this) after which you'd switch to a periodic tenancy and only have to give one month's notice.
A buy to let mortgage is usually around 85% of value but the lender would look at what the rental on the property would be. There's a few people on here who have taken out buy to lets more recently than me and would have more recent experience of this.