Oooh, what an interesting thread, I just joined the forum to find out I'm already being recommended, thanks Kanisha
Rosemary, handspinning isn't necessarily that expensive. If the fleeces are clean and free of straw etc, and don't need much preparation then handspinning will work out at much less than £4 per oz. Of course it depends on the thickness you want the yarn. Obviously 1kg of laceweight will take much longer to spin than 1kg of chunky. I work on an hourly rate rather than by weight as it is the fairest way for the customer and for myself.
Out of a recent batch of Ouessant which I spun the yield was about 75% of the weight of the raw fleece. Also bear in mind that if you do send your fleeces to a mill in a batch with someone elses you will not be getting back your own wool but a mixture of yours and someone elses, which doesn't sound like what you wanted.
I hope this is of some help, if you need any more advice or decide to go for handspun I would be happy to help if I can.
Diane