Thanks guys for the tips. Unfortunately from the calls I have made it looks like about $75 including all cabcharge/credit card fees. Considering a cab is only costing me $45-50 all inclusive I don't know if I can justify 65% increase in cost. Saying that it is all claimed back through my company but just not sure if the person who approves my claims will question me as to the rise in cost!
I guess this is the problem with living so close to the airport! If I was going to the city or my companies office in South Melbourne it would be a no brainer.
I have started using allhirecars.com.au booking through their website and prepaying. It is not the same driver or car every time but so far the service has been brilliant. Last week I managed to get on an earlier flight and just gave them a call as I was boarding, an hour later when I arrived in MEL the driver was there waiting for me. Is only $60 from the airport to my place in Brunswick West, not sure to Southbank.