Well, whether or not it was wise to buy a hive "because you saw one on ebay" is a moot point. you have it now, and unless you want to go through the hassle of sending it back, let us assume "That it is a good 'un". If it falls apart, glue and pins will be the order of the day, but let's assume it wont.
Basically if you measure the frames:
"Nationals" should be about 356mm [14 in] (Bottom bar).
"Langstroths" should be about 447mm [17.5 in] (Bottom bar).
I say "Bottom Bar" because that is the "Size of hole" they need to go in, so alternatively you could measure inside the hive between "the shelves" (the bit where the lugs sit on to hold the frames up). Inside the hive mind, not "with the shelves", with the Shelves will give you a "Top bar" measurement.
Nationals have "longer lugs" (~38mm I think).
Langstroths and "Commercials" have shorter lugs (~18mm) (Commercials may be 16mm)
So that measurement (inside the hive) should be:
For a National ~370mm
For a Langstroth ~460mm
One or the other, should make it fairly obvious.
The "Depth" of the boxes determines which exact frame you need.
In my view, it doesn't really matter what you have, but it will make a difference when you come to populate it. Although all my stuff is National, now I know what I know, I would have gone Langstroth.
Why? Because Langstroth is the original and we should ALL have stuck with that, everything should be Langstroth. But we "British", we have the idea that we know best and invented the "National", which is a much smaller frame than the Langstroth. This may have made sense at the time in that our "British" bees may be less prolific than other Bees and so this may have been a better fit 100 years ago. But now everything is so interbred, that the beekeeping community should move to a "Single Standard".
Anyway, you'll have one or the other.
Bees.
When you come to get your bees, you may wish to buy them, or join your local association, where it is 50/50 bet that, if you join now and do the course, by the time spring comes, some nice soul is likely to say "Here, here's a few bees". Beekeeping associations, by there nature, are not terribly commercial, they are very supportive though. (For instance, my local BKA has extractors, wax melters, Varroa vaping tools and all sorts available free, this could save you a good lot of money).
If you buy bees, find a supplier who will supply them on frames that fit your hive (they are out there).
Or you could just let some Bees move in, they will if you ask them
