if you're going contracting - www.ecomrecruitment.com are the best at arranging contracts in London i've found. I've worked with them several times, they're a pain in the arse, there are like 10 of them and they don't talk to each other and have different clients but they have the best contacts and they work really quickly on arranging contracts so you're unlikely to be out of work for long. Might be worth talking to them when you're back from SA :)

otherwise Aquent and Datascope are good agencies for .Net developers.

Goodluck