I just got a quote for replacing 2 lengths (about 7m total), no mitred corners but cut out for sink and gas hob. £200 labour and cost of worktops (£250). Am in London though and there seems to be a big North/south divide for labour costs!
I got approx 5m of IKEA solid wood worktop fitted for £120, 3 years ago. This included insetting the sink and gas hob, one mitred corner, and a fiddly bit to fit round the chimney breast of the old fireplace. (Yorkshire tho!)
I paid £200 as a day rate for someone to fit my wood work tops. About 6 metres, cut out for hob, joining a breakfast bar bit and doing a lovely job of rounding off all the edges. Also did all the upstands. Took a full day to do but he was really good. I'm in the northwest.