Setting up DNS records for mail and website

[#1]

I wonder if anyone can help with this small setup issue...
If I want to configure the dns records of my domain (which is hosted by plusnet) to do the following:
1: Point www.mydomain.com to my public IP address provided by plus net, so I can host my own site on my own webserver.
2: Have any mail sent to me@mydomain.com delivered to my default plusnet mail box.
What settings should I make in the "Additional DNS records (Advanced)" section of the Domain Name Manager to achieve this?
Cheers Bill.

[#2]

http://usertools.plus.net/tutorials/id/14 should answer item 1
Basically its:
www A <blank> youripaddress
For item 2 this is not a DNS change but a mail config change. PlusNet mail does not have separate mailboxes for your username.plus.com or domain email addresses. me@domain.com is actually the same mailbox as me@username.plus.com. By default, any mail that is sent to a mail address for which you have not set up a separate mailbox or alias automatically gets delivered to your default mailbox.

[#3]

Cheers for that Peter.
Just to confirm, at present my email works just fine.
All mail is handled by plusnet, so for example if you were to email me at bill@mydomain.com I would be able to login to the "Squirrel Mail" and see your message. Just how I want to keep it.
Now if I add the entry "www A <blank> myipaddress" to the dns table and do nothing else at all, this will cover item 1 of original post and leave the email working as is?
(As an aside there is already a record in the table of:
<blank> mx  20  mx.last.plus.net.
I guess this is the current email record)?

[#4]

Yep, all correct. The MX record is a backup mail server for receiving email to PlusNets mail servers if the main ones do not respond to a connection, and is added by default by PN.