There doesnt seem to be a definitive answer on the searches I've done? I managed to get a written off '98 modeo (only genuine 33k miles) for £250. Seemed to much of a bargain to miss, but obviously this needs a catlytic converter as its post '95. But does it definitely need fuel injection ?

As far as i understand the problem with running the catalyst is that you have to have very good mixture control which is where efi comes in. I was once told that carbs like twin 45s like to run a bit richer and that this will destroy the cat over time.
I think the simple solution if you want to run this engine with carbs is to run it without a cat for every day but have a bit of exhaust that you can swap out and replace with the cat when MOT time comes.

I don't really know much but I'd imagine the EFI system will have a lamda sensor and perform emmisions control functions. It may well be possible to tune carbs correctly so that this isn't required though, but it'd need to be done professionally on a rolling road I think.

Why not fit injection and a cat? There are a few options you can go for and cats are coming down in price and can be fitted within a standard lowcost/7 style exhaust. You will also get the benifits of injection with better running and in most cases more power. The best bit must be that you will have no worries about SVA/MOT pass now or in the future.