I use a Three Network for my laptop, when I am in my caravan in Cornwall. It costs me about £10 for 1-2 weeks use. It works very well indeed.
I can't remember how much the dongle cost but I don't think it was very much.
I bought it from Currys ( I think ! ) Its very simple to use. But whether Three is the right one for Deal in Kent I am not sure of. Go to their website, put your British Postcode in and see what they say. Some ISPs will have better coverage than others and they will all offer a PAYG dongle service.
But you may be able to pick up a neighbours wifi. There are also plenty of places
that offer free wifi these days....McDonalds, Wetherspoon Pubs, etc.
Let us kn ow how you get on...we always appreciate feedback here on AB !