If I bought an all-in-one printer, copier and fax, could I send faxes just by connecting it to my normal BT landline or is there a special sort of line I would need?

No, you can send faxes via a standard telephone line nothing special required.

Thanks for the reply. How would the cost of sending the fax be charged e.g. local call rate, national rate etc

it's exactly the same as a phone call, nothing special.

Faxes are sent just like normal voice calls. To the system they are voice calls. The fax machine turns the data into audio and squeals it down the line where the other fax machine turns it back into data.

If you are sending a fax to an 01 or 02 number then you will be charged whatever rate your provider charges for calls to such numbers.

From BT that is:

3p / min daytime + 3p connection, per minute billing, so a 45 second fax would could 6p.

5.5p for up to an hour evening and weekends.

BT charges the same rate to an 01 or 02 number whether local or national.

Other providers (except cable) are cheaper, cable line are dearer.

Thanks for the replies guys, that is very helpful.