I personally would do exactly as you're proposing. Don't under-quote and (definately for the first few jobs, until you've sussed it out) be prepared to spend on outside help to make a good product.
I know when I moved into telly-vishon a few years ago I listened to those who had "been there, done that, got the T-shirt" and kept my rates high (you can always "do a discount" to get a job but if your rates are low and you get a punter with a thick wallet, you can't suddenly increase your rates.). If I have to supply a crew, then I've learnt that it pays to spend money on good assistants, soundies etc. in the long run.
A good tip now... Get in touch with the local college or university, the student union will have a noticeboard, and put up a notice "Occasional help with video projects wanted, a fiver per hour" and collect a few telephone numbers of those you think you can work with. Having a "bag carrier" on a job who can help with moving lights and furniture, get the stuff you left in the car, and generally take the mundane jobs off your shoulders is worth it. Incidentally another word for a bag carrier is a "grip". Having a "grip" on a shoot really lets you concentrate on the job in hand without having to worry about feeding the parking meter, finding electrical sockets etc. etc.
It really is fifty quid well spent (and impresses the clients too).