Both scopes are compatible with the same eyepieces... what fits one, fits the other. You get greater magnification from the same eyepiece on the bigger scope.
I'd buy a used one from a dealer - there's usually one or two knocking about - you might get the balance of the original warranty from Opticron, but you'll certainly get a warranty from the dealer. But you'll know straight away if there is anything wrong with the scope, and it's such a small world, I doubt any of them will send something that isn't right. Try Ace Optics, The Birders Store, Bass and Bligh, WEX, MPB and Ffordes.
As for a bundle, I assume you mean with eyepiece, but if you're also attracted by a fitted case I wouldn't worry too much about it, if it's not part of the deal. They're pretty expensive and used ones come up on eBay and here on the forum.
As for which one. Depends on budget, how much weight you want to carry and how much 'reach' you need from a scope. I'm guessing in West Wales you might be watching a lot of sea birds, in which case you might want the bigger scope for greater magnification... to get you closer, in effect. The bigger scope will allow more light through the front (objective) lens, so it'll be brighter when the light is less than ideal, say at dawn and dusk, but in good light you won't notice any difference.
I've had both scopes. The 60mm does not have a built-in hood, which really annoyed me when looking anywhere near the direction of the sun. You can make your own of course, Blue Peter style. They both have the best value / performance ratio of any scopes on the market in their size. I'd suggest starting with a 60mm, as you're most likely to take it with you, and if it's been bought used you'll lose little, if anything, if you step up to the 77mm.
Then there is angled vs straight. My guess is that 80% of birders go with angled (might be more), but both scopes have a rotating collar, so if you're looking down at sea birds on cliffs, you can twist an angled scope to find a comfortable viewpoint. Angled is easier if you're looking up into trees - means you don't have to set the scope too high on a tripod - giving you a better choice of tripods.
Hope that helps.
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