My latest pc comes from PC World and very happy with it.
However i also have a couple of machines from Dell and i think this maybe your best bet for your needs.
You will not need the £1000 budget.
Regarding the modem broadband setup,your choosen provider normally supplies these for free.
click here add the os and monitor and you will have spent the £1000 from the Novatech link.
These are justt ideas and im sure others will add to it.