Yes they fit any size. The only thing you need to watch is that the one you choose will fit suitably over/between your windows and door, you would not want it ending up half way across a window. Yes , I have seen one fitted like that !!!
Porches often come in 3 sizes, Mini, Midi and Maxi, so it all depends how big you want it and what suits your van best.
I think you also need to get the correct height. Some caravans are taller than others. I had a look at the NR site and they sell them in 7', 7'6 and 8' heights. Have a look Awnings
Take care over the height of the Porch.My Avondale has a very low awwning rail so most don't fit, however Isabella make a special Minor(low) Porch to fit. The downside is that it is only available in Burgandy. I have not used mine yet as I only bought in December ,privately, second hand from an advert in Practical Caravan.
I dont think you will have the same problem with a Swift.
Ours is a Trio Midi. Because of the design the height is not an issue. Super awning but a real pain to put up. We also have a Fiamma Caravanstore. Great for short stops. We have 2 side panels and a front/extension. Since getting it we have hardly used the porch. Only good in summer/nice weather though. Think Italian climate !!
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