I called Skunk2 on Skype in the evening (8 hours time difference), was on the phone to a chap there for about 20 mins (cost me less than a quid).
A fascintating conversation, seems I'm right. Their stage 1 camhafts have slight increases in lift and duration but not overlap, stage 2 more increase in lift and duration and some increase in overlap, stage 3 even more than stage 2. He said that the lift on stage 3 is so aggressive, that pistons with a more concave crown would be a good idea. He said that there are two main types of head for K-series engine: the 3-stage VTEC and the 2-stage VTEC. The camshafts are different, and the 2-stage VTEC heads are on engines made more for economy than power (sounds like the K24A3 engine).
He said that it takes their mechanics 15 minutes to change both camshafts on an engine. He said that valve springs can be changed without removing the head but you need a special type of spring compressor, and the procedure is to move the piston to TDC then slightly presurise with an airline through the spark plug hole to keep the valves up (FWIW I've only ever done valve springs myself 35 years ago with the head removed).
Regarding ECU, he said that whilst it might be possible to fit a stage 1 camshaft without a remap, it's best to get an aftermarket ECU anyway before doing any of this. He also agreed when I said that the K20 was probably a better engine to mod than the K24, indeed he said that there is a new Civic in the USA with a K24, which everyone was excited about, but it's a disappointment. He also agreed when I said that the K20 head can pass higher volumes of air than the K24 head (I read that on this forum). He said that it is possible to fit a K20 head to a K24 block with minor mods to fitments, but it would be a good idea to change pistons (concave etc) while one was at it. He also agreed that the Hondata ECU's are an easier job on the K20 than the K24.
So, I would say to anyone thinking of buying a petrol Accord with a K-series engine
1. if you think that you will never mod the engine, go for the K24
2. if you think that you will mod the engine in the future, go for the K20
Basically the K20 is easier to mod and has the ability to give much higher HP than the K24.
But to answer the question Steve ...yes, but best to get an aftermarket ECU first (and I'm 100% up for that, I'd love to find a piggy-back ECU and wire it in myself)
Anyone want to swap a K24 for a K20 btw
edit: btw I think the pistons can be changed on these engines with the block in the car, and fortunately these blocks have dry-liners so head removal will be straightforward ... the idea of removing the head from a wet-liner block would scare me to death