Does the bike already have 700c wheels? If so, then all you need is rear wheel with a flip flop hub. Even if they're 27" wheels, 700c should fit with the worst case scenario being you need to find a longer reach brake. If you put a 700c wheel on the back and keep the 27" wheel on the front, the bike will work just fine and you won't even be able to notice by looking at it.

I've used this wheel on my main fixed ride for a couple of years with no problems.

As for spacing, what you seem to have is standard vintage road spacing. A track wheelset should fit just fine.

Steel frames can be manipulated too. If you choose to get a wheel with a 130mm Surly hub there's a procedure called cold setting which is a fancy way of describing the act of bending your frame with a 2x4.

With an old Raleigh, you might have an issue with the front fork. The ones made in Nottingham had smaller dropouts. Worst case scenario, you keep the original front wheel or take a file to fork dropout so that the axle fits. But if it has 700c wheels, I'm pretty sure that's not the case.

So the bottom line is go out and buy any wheelset you want.