New user - printer won't work?

[#1]

I am new to Plusnet broadband and have little technical expertise - please help!
We have a completely wired system, with a TG582n router, 3 inputs (main computer, network printer, hub) and a hub (3 other local network computers). All the pcs are Windows XP. We set it all up 2 days ago and had broadband and access to the network printer for all the pcs. Everything was good ...
Today we still have broadband, but are unable to print from any of the pcs. All the lights are on, the printer can print internal stuff, and all cables seem OK. I have re-installed the printer on the main pc, re-booted, and re-set the router, but nothing seems to work.
A call to the Plusnet guys merely confirmed that the broadband was working OK, they are unable to support other issues, which I suppose is fair enough.
Can anyone help?

[#2]

Has the IP address of the printer changed?  I'd suggest setting it manually to an address outside the DHCP range allocated by the router.
HTH

[#3]

Oh dear, there's so much in your reply I don't understand!
How would I change the IP address of the printer, and how do I know what range the router is using?
Many thanks for your help

[#4]

Right, I have pulled myself together and googled how to find IP addresses. 
The printer is plugged directly into the router, it's not attached to any particular pc. However, looking under installed printers on this pc I can see the IP address of the network printer (per the pc) is 192.168.1.12.
On the printer itself, going through the menu settings to TCP/IP, it shows 192.168.1.64.
I'm guessing that these 2 numbers should be the same? Can I change the setting on the printer to match that on the pc? What about the DHCP range you referred to?
Thanks for any help on this.

[#5]

Decided to go for it
Changed the IP address on the printer

and IT WORKS !!!
Thank you so much.

[#6]

The router can hand out IP addresses to any machine that asks for one - This is called DHCP (Dynamic Host Configuration Protocol).  This is generally a 'good thing' for PCs etc that come and go but not good for fixed resources, like printers, that you always want to find in the same place.  I think the default DHCP address range for the Technicolor router is 192.168.1.64-192.168.1.100.
It looks like your printer is set to get an address via DHCP (possibly called 'Automatically') as that's how it now as the .64 address.  There should be a setup option to manually specify and address so this will allow you to put in:
IP address: 192.168.1.12
Subnet mask: 255.255.255.0
Gateway: 192.168.1.254
Assuming that the printer is capable of downloading firmware updates etc, this should be enough of a config to get you back up and running.
Edit:  I see you've found the option

[#7]

Thank you very much for taking the time to explain things.
I had thought it was a router problem but realise now it was down to the printer settings - looking at the printer manual, the factory setting of "Enable DHCP" is ON so it was indeed asking to be assigned a new IP address when it was switched on.
By manually changing the IP address (as done yesterday) the Enable DHCP is turned OFF so the problem shouldn't recur.
I'm learning!
Thanks again