PC what's it like.

Very much so, it's a great CPU and a decent midrange GPU. Should be able to handle anything at high settings.

The same pc is listed on ebay right now, also for £700. If you go through gumtree the seller avoids ebay + paypal fees (10% and 3.5%) of £95. He should be more than happy to drop to £620 or so via gumtree

Edit: and yes, its small form factor, I had a quick look at the specs and it's not that much bigger than an xbox one