Indeed. You'd have to start with countries where there is a known problem so that would be anyone arriving from affected African countires. There would also be an argument for any country where there are cases being treated and containment has failed (which would, at the moment be Spain). Ultimately though, unless the government is willing to basically shut down every single access point to the UK and stick enough troops at each one to make damn sure nobody sneaks in (through the Channel Tunnel for example) any attempt at isolation is doomed to failure.

That's kind of the point I was going for - to stand any genuine chance of stopping Ebola, or other pathogen, from entering the country with border controls you'd have to take such draconian measures (and have taken them before the problem spreads from its initial location) that you'd basically shut down the entire country. Arguably, if things were genuinely that bad, the problem would probably already have gotten past the border anyway.

The current measures aren't likley to actually catch anyone who's been infected from entering the country - it's a PR exercise at best, although a worth while one to minimise the risk of panic. The real measures to prevent the spread of Ebola in a developed country are actually front line medical services and I'll leave it to you to decide how well they'd actually cope if the someone with Ebola actually staggered into an A&E department or GP surgery.