One method which would allow you to use same email address all the time but still use whichever local free ISP you like is to use someone like
www.123reg.co.uk to register a domain, they vary in price but the cheapest is .co.uk for £2.89 per year. You can manage your domain on the net and can set e-mail forwarding for up to 100 email adresses at your domain to forward email sent to your domain to any other email account you wish, all included in the price!
I have used this service for some time now as free isp's come and go and I got fed up of advising everyone of my change of e-mail address.
Hope this helps.