I travelled through from Malawi to Zambia via Chipata in 2001. Things change so check with your embassy..
http://www.africaguide.com/country/zambia/offices.htm
We were able to purchase Zambian visas at the border post although they were rather expensive at US$60 per. We had problems because they wanted to see our yellow fever vaccination cards even though they are not required (the guy was after a bribe) we eventually got through without bribery but it was a big hassle so go and get your vaccine card beforehand.
Make sure you have front (white) and back reflectors (red) on your bikes as the Zambian cops use the lack of them as an excuse to fine you.
There was a good camping site about 2-5 km from the border on the right called chicken something or other (I cant remember) and Chipata is actually about 10 km from the border.
Currency was available in Chipata through the backdoor <img src="[
www.africaguide.com]] but avoid it as the banks gave a better rate.
I am also a Brit.
Hope that helps.
Phil
moderator