If all of the attacks are coming from one IP address you should be able to block that IP address with your firewall. There should be an option init to add IP addresses to a exclusion list, this will prevent that IP address from ever being able to connect to you.
Alternatively goto http://www.samspade.org towards the bottom there is a box to the left of a button that says 'IP Whois' copy & paste the IP address in here and click on the button. This will tell you where it's coming from.
I've just done a quick search and it's coming from Energis UK. Scroll down and you'll find 'Abuse reports to
[email protected] please!' send them a poilte email giving all of the information that your firewall is reporting, Time, Time Zone (i.e. GMT), Date, Type of attack, your IP address, their IP address. Once they've been able to verify the attack they will do something about it, usually they cancel that persons subscription to the ISP. If they find that it's not come from them they will forward it on to the correct ISP for you. This is an example of the type of thing you need to send them, by all means use it.
Example.
To whom it may concern,
Dear Sir/Madam
I have had an attempted unauthorised access to my personal computer originating from your netrange. I would ask if you might be able to resolve this issue at source. Please find below all the information I have regarding this matter. If you are unable to help with this problem would you please email me with any contact addresses where I might be able to find the help I need.
Date: 23/02/2003 Time: 10:54:07 GMT
Rule "Default Block Backdoor/SubSeven Trojan horse" blocked (work(217.46.167.220),27374).
Details: Inbound TCP connection
Local address,service is (work(217.46.167.220),27374)
Remote address,service is (217.226.43.145,2294)
Process name is "N/A"
Yours sincerely,
Mr *******
I hope this helps.