If you want your own domain name go to someone like
UK2.net and buy it. Then when you set up with iweb, they tell you the servers to point your domain at, you put them into uk2 and it changes in about 24 hours. Then off you go.
I think I web will buy them for you, but it's not something the do on line or as ruthlessly efficiently as a company like uk2. Looking at their site it looks like it is really part of the corporate rates. The cheapest with a .co.uk name hosting is £10 a month. UK2 will register a .co.uk for £5 for 2 years (and I got charged a £3.98 registration fee, though it looks like they have reduced that now.
So just need to choose a name now. For £8.98 + £10.69 you will have your email worries sorted for 12 months.