I think I would disagree about most 147s having Leather, even with a Lusso spec car.
I was looking for about 6 months before settling on mine and the vast majority seemed to me to have cloth interiors. This may however just have been the case for the age of car that fell into my price range as I was looking for Lusso spec cars around the 02 - 52 age. Perhaps Leather became more popular on later cars approaching the facelift?
Lusso spec was top of my wish list (more so than the choice of 1.6 or 2 litre!) as it meant Climate control (a must), driver's arm rest & lumbar support, CD player + other things I can't remember at the moment.
Leather was on my list of wants but was less common or commanded a higher premium (not necessarily because of the leather but because, as an option, people appear to have ordered it along with other upgrades and it tended to be on the higher spec 2.0 cars which I originally shrank away from!). Certainly putting Leather into the search field on Autotrader seriously cut down the choice of cars available. In fact most of them came back as Selespeed versions which is perhaps why Marko has this impression.
Anyway, I don't see why 147 seats wouldn't be universal from a fit point of view. There will of course be differences between 3 and 5 door (folding front seats etc) + there are other more subtle differences which are linked to the lusso spec and the comfort and winter option packs. These include;
1) Front driver seat lumber support (Lusso)
2) Front seat centre arm-rest (Lusso)
3) Heated seat options (winter pack)
4) Adjustable height on passenger seat (option)
5) Fold down bolster on rear seat (comfort pack, I think)
I would have thought though, that apart from the Heated seats, which will require the approriate wiring loom connections, they would all fit the same standard 147 layout and fixing locations.
The alternative would be to get the seats covered by an aftermarket upholsterer. Not sure which would be cheaper. I suspect EBay by the looks of a couple of auctions I saw recently.
Be careful that the sets on ebay or from breakers don't have accident damage. I shoudl imagine that repairing the seams around Airbag damage + the cost of new Airbags themselves would be costly. You might be aswell to pay the extra to get a car with leather already fitted.
In the end I opted for a slightly older model to get the options, colour leather that I wanted. It all comes down to compromise and what is more important to you from the car. Of course, it also depends on whether you are planning to buy a new one!
Happy hunting. I had a Fiesta for 7 years and in buying my Alfa I finally feel that I've grown up.