Hi... happy to work with you on this task. I've done a lot of webservice integrations in the past of various flavours. I'm assuming this is a server-based program (ASP.Net or Windows service/app) and as such, although the interface content is JSON, there's no actual JavaScript involved. Essentially all we need to determine is exactly what BetFair need sent over the wire, then create that.
As you can see, I'm based in the UK and have a long history with Freelancer and its predecessors. I've not worked through such sites recently as have been working with 2 or 3 major clients who kept me fully occupied; now have time available and therefore looking for new projects.
Don't hesitate to contact me for any further clarification.