Do I really need to configure my server with a public static IP address?

I'm setting a few sites up and many email accounts for a new company so I wanted to save some money as I already have a server running Windows Server 2008 R2.

I have a static IP of 80.229.46.115 and the server's IP is configured as 192.168.1.63. The server is at a business address and is using business broadband. Upon asking 123-reg.co.uk to add an A record for my FQA they have informed me I should not be using 192.168.1.63 under IPv4 settings manually and I should be using the actual static IP of 80.229.46.115.

When I try to add 80.229.46.115 under IPv4 it loses connectivity and under the machine's IP of 192.168.1.63 I am seeing the DNS server is running OK.

Is what the rep at 123-reg told me incorrect?

Yes, the rep is correct. 192.168.0.0/16 is a private IP range, and isn't available to the public Internet.

What you will need to do is use your public IP in the DNS record and then port-forward to one of your private IP addresses.

My personal advice, though, is to NOT use home Internet/networking for business use. What happens when your home broadband service or phone line goes down? Is your customer happy with having their data hosted on a residential premesis? How good is your home security (as well as your home network security)?