Re: "But don't you have to pay another £70 to do so?"
The current situation is that the conversion to Win 10 Pro will remain free until Dec 31, 2017. Thereafter it will cost $49. (At current rate of exchange plus VAT my guesstimate is that the price in the UK will likely be about £50*)
* Which is chicken feed compared with what this device costs in the first place. Anyone who has got the spons for this lappie is not going to give shit about en extra 50 notes or so representing as it does about 2% of the price of the 500 Gb version.