Dieffe :
you need ram too, skylake need ddr4 and with 200£ is hard. i5-6500 is the only worth (i5-6400 has a clock speed too low) and cost £160 at least, then u need 50£ for a entry level mobo like the asrock h110 plus 8gb of ram. Otherwise you should stay on Haswell Architecture but it's dead and abandoned with no possibilities to upgrade in the future without changing everything again. Skylake and LGA 1151 is going to be used for next generation too.
Just to clarify, 2.7 Ghz on the i5-6400 looks low, but It's turbo frequency is 3.3 Ghz. Which is alright.
And yeah, It's true. DDR3 RAM is not officially supported with Skylake, so DDR4 RAM is recommended:
http://wccftech.com/skylake-does-not-support-ddr3-damage-ddr3l-only/
So Skylake isn't possible within 200 quid, this is the best you can do with Haswell:
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i5-4460 3.2GHz Quad-Core Processor (£149.99 @ Novatech)
Motherboard: Gigabyte GA-B85M-D3H Micro ATX LGA1150 Motherboard (£53.68 @ More Computers)
Total: £203.67
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-03-20 18:42 GMT+0000