I absolutely agree with Chris about the New Inn. My girlfriend and I have only been there on a Sunday, but they do a great Sunday lunch. The service is friendly, the atmosphere is relaxed and the food is very good. It makes a pleasant change to see a chef who evidently enjoys meeting his customers (once all the orders have been sent out, of course). I once knew a restaurant where the chef viewed his customers with utter contempt.
If anyone reading this is thinking of going, a few words of advice. Firstly, it is much more of a restaurant than a pub, despite the name, so don't go there expecting to play pool or darts. Secondly, it's only open 12-3pm for Sunday lunch, so don't do what we did and turn up at 3.15pm hoping for a quick drink. There are no other pubs nearby either. (We were out for a walk and thought we might be able to stop off there, so we took a 20 minute detour into Etchinghill. Incidentally, I would not recommend to anyone without a death wish walking into Etchinghill from the road from Folkestone, because there's a very nasty 350yd stretch of road, with no pavement and no verges, down which some cars hurtle at about 50mph.) Finally, I'd recommend that you book, because it's very popular (at least on a Sunday). We've managed to get away without booking before but only just, and we'll be booking next time.
Bear those things in mind and you'll have a lovely time.
This is my site The 'Gerald that I set up in a fury of excitement when I first came to Folkestone sometime in '04. I'd been a frequent visitor for a few years previous to that but I am technically one of those Down From Londons you get nowadays. The site used to be updated more frequently with a calendar of events and voting for best venues + things, and I know it was a handy resource for those who were moving here. Now I've moved out of Folkestone again (though only a couple of miles) it doesn't get as much attention as it used to. Ironic really as The town is becoming the exciting place we always thought it was about to become. My name is not Gerald by the way, this comes from the name of a fake newspaper in an episode of Brasseye or something, the Portsmouth Gerald, and how there is a local newspaper here called the Folkestone Herald. Puns like this are great aren't they? Do contact me if you have anything to offer, email anythign @ this domain, or try @folkestone or @pauly on the twitter.