Ok. I think we're trying to square too many circles here Meg. If you know what I mean. Needs a bit of lateral thinking.
Having a manufacturer tool-up especially for a one-off would be horrendously expensive.
Have a look at this for example...........
http://www.qssupplies.co.uk/bathroom-furniture-shower-taps/72388.htm
465 x 335mm.
I doubt if you'll ever find an inset that's not only small enough, but has 2 tapholes. One with no holes may be the answer.
An oak top rules out completely having taps mounted on it. Eventually, the oak would stain terribly, unless you're very lucky.
The inset in my link would look great with a single spout horizontally projecting from the wall behind. A simple lever operated valve could be mounted next to it (built-in of course - just some excavation in the wall behind.)
I know you've already bought the taps, but don't let that rule you. Most single, even mixer taps can be converted to levers.