DNS & External Hosting

[#1]

Hi folks,
I have a dedicated server that I'd like to point my domain name at instead of ccgi, but I can't seem to get it working correctly. Two questions:
1) What exactly do I have to change to make the domain point to the new server? I was under the impression that simply changing the right field of the A record in the domain settings manager would make this happen, but as of today it's still pointing at PlusNet's IP. Is something wrong or is it just a case of a long propagation time (currently about 18 hours since I made the change)?
2) I also set my mail delivery options to "Other", expecting the MX record for mx.last.plus.net to pick up the email as normal, but this just seemed to lose email until I set it back. What's going on here?
My current DNS entries are:

mydomain.co.uk.	A		[new server IP]
www.mydomain.co.uk.	A		[new server IP]
	MX	15	mydomain.co.uk.
	MX	20	mx.last.plus.net.

Any clues anyone?

[#2]

Hey drbenway,
I have made a small change to the settings for the domain and this should update in the next four hours, looks like the control panel simply hasn't updated properly 

[#3]

Thanks, you're a star
I'll let you know if it works.