Thank you for the quick reply.
So the little green component with the 2 sodler tabs on either side is the on-board antenna, I would have to somehow remove it.
The pads you mention next to the ICSP header are the pads either side of the little circle that the on-board antenna seems to be connected to?
Unfortunately I can't relate the schematic (where I found X1 & X4) to the actual WiFi board, are the 2 tabs where I must put the external antenna onto, or are the 2 tabs a common point, and where the circle on the board is, that is the other connection?
Looking at a different WiFi board, the threaded part of the connector is soldered in 2 places (although still common), and the centre pin soldered to a second point. Excuse me if what I'm explaining is incorrect, I don't know much about antennas, and why it needs 2 connections confuses me too.