Is it possible to purchase a domain name and have a control panel with it without having webspace from you. The reason is because we may be changing our internet provider and my Wife has her tiscali e-mail address, so if she brought a domain name, she would then have her own personal e-mail address with that domain that can be pointed to whatever service provider we are using at that time.
Your idea is sound. If you purchase a domain from say http://www.fasthosts.co.uk
both of them provide free email forwarding which will achieve what you are after.
They do not provide any anti-spam on email-forwarding. That will have to be done by your new ISP.
BCA WebServices does not offer the option of updating email-forwards without a control panel so it will be cheaper for you to deal directly with FastHosts or 123-Reg or whoever you choose.
At a later date you can easily point your new domain at a BCA hosted website if you desire.