Replacing concrete paving slabs with natural stone

[NovicePaver]

I've got about 16 sq m of plain concrete slabs 45cm * 45 cm. I'd like to replace these with some more attractive Natural stone slabs and extend the area by another 4 metres to approx 20 sq m.
The existing slabs are quite solid and appear to have been laid on a weak mortar mix.
As the new natural stone flags are quite expensive approx £33 per sq m , I'd like to get a professional in to lay them.
I'm happy to remove the existing slabs myself, along with approx 2" of the old mortar mix , so all that needs to be done is mix the mortar and lay the slabs and grout them.
Assuming this sounds like a reasonable plan , how much would you expect this to cost for
1. The labour?
2. The materials , ie mortar and pointing?

How long would this take a skilled person?

Also in this situation where would I lay the sheet of material to stop weeds growing, (under the mortar I presume?)

Any help gratefully appreciated.

[Tony McC]

I can't comment on prices as they vary so much throughout the country and, as this is such a small project (relatively speaking), standard pricing is inappropriate - the work need sto be seen, surveyed and then costed when all relevant factors have been assessed.

As for timesacle - not more than a couple of days, I'd reckon.