[Asterisk-Users] A new pbx for an office in the UK

[Steve B]

My office is wanting to replace their pbx as it doesn't support enough extensions. They have 8 incoming lines, one of which are dedicated to alarms and one is for the fax machine. The other 6 are for the ordinary phones. They have about 10 analog extensions but want to increase this to about 20.

They've been quoted about £4500 for a new pbx.

My question is could I use Asterisk to do this cheaper? What hardware would I need? and would this work in the UK? And, perhaps, what else do I need to know about their present set up in order to ask the right questions?

I know little about phone systems but I am familiar with programming and network administration (Linux & Windows).

TIA,
Steve