Office Move and needing help with VOIP questions please.

[jhb04]

Hi,
We are moving office to a managed building and the charges for their BT lines are rather ridiculous, so we are looking at moving to VOIP as a cost effective solution but don't know where to start. We could do with someone to come here and speak to us about what is available and what we need etc. Does anyone know of a company who do consultations?
Just as an idea of some of our concerns, please see below:

Currently we have 1 main number with 6 lines available, so potentially we can accept 6 calls from that 1 number at any one time and the clients would not get an engaged tone unless all 6 lines were already busy. Is this possible with VOIP system, and what would we require?

We also have a seperate number that a call centre use to contact us on for support. These calls go to two particular handsets which ring simultaneously, but again can be transferred as needed. This is something we would also require but no idea whether it'd be available or how it'd work?

Any help would be much appreciated. Assume we know very little about setting up VOIP!
Thanks.