Advice on buying first bike... eBay

provenrad It sounds like a 700c will fit. You may have a couple of issues to watsh out for:
1 - properly adjusting your front brake, especially if you go for narrow roadie rims
2 - Width of regular rear track hubs is 120mm, your frame is 135mm.
You can get 135 fixed hubs from on-one / goldtec / others, but then won't be able to use the wheels on another frame.. unless you get a nicer $$ hub (goldtec?) where re-spacing kits are available to swap later.
That Courier comp is a solid machine, I personally would not choose lightweight wheels, but something like a 700c touring rim? but it really depends how heavily / badly you ride it.
If you go to evans you may regret it after getting thus far.. and they will think you are crazy.

Yep I agree.

RE 1. you will not beable to use the cantilever brakes but a long reach caliper brake should work fine. Get some washers to respace the rear hub out a little.

The only problem you may have is with chain ring clearance on a mbt for a 42 mm chainline depending on the size of chain ring you use. You can always get round this problem by crimping the chainstay.