Aqua on the waterfront just along from my office should fit the bill, though I noticed today they appear to be having some refitting work done so best to check they'll be open. About 15 mins walk from the station, 5 mins in a taxi.
The Glass Boat just along the water is also great, though not sure about the sitting around for a few hours after the meal, they tend to be quite keen on getting rid of you once you've finished your meal.
If quality / choice of food is not so important, the Banco Lounge up on the Wells Rd (15 mins walk from station the other way) has free wi-fi and you can sit in there all day, no worries. It's a bar rather than restaraunt, hence food not up to standards of the other two I mentioned, but it's perfectly acceptable and it's a nice relaxed atmosphere.
If you want any more ideas pm me.