I'll be honest on this subject now,
When you're doing domestic you can charge whatever you think you'll get away with,
But on commercial its a totally different ball game, unless you're well in with the client, or can offer a service that nobody else can realistically provide, you need to be charging a realistic price where you can make money and be happy. Charging high and getting the quote accepted is all well and good, but unless you've got it all signed up on a contract then you're going to be a sitting duck waiting for somebody to come and under cut you.
What I'm saying overall, is to provide a fair price, do a decent job and you won't go far wrong. £300 per man day isn't something that is going to realistically happen day in, day out on commercial work. And to be honest I'm glad that it isn't, like I said previously if that was the case I'd just be waiting for the phone call to terminate us as the client had found somebody cheaper. Don't get me wrong, it can be achieved, sometimes even more, but if you're using those type of figures as a pricing structure then you won't be keeping very busy.
Dean.