yikes
where to start.....
first if your looking for a sporter to fix up you need to find one that the metal has not been cut.
No1 MkIII and MKIII* aka ShTLE or SMLE are less likely to have the barrel cut, but harder to find all the other parts.
No4 Mk1 and Mk1* have a slight difference between stocks as well as the Mk2 MkI/2 and MkI/3 will also have differences. However the Mk2 and MkI/2 use the same stock. These marks of rifles are more likely to have the last 2" of barrel cut off to remove the bayonet lugs, making them poor candidates for restoration.
No5 Mk1 aka jungle carbines are easy, mostly because they were not full wood stocks so they didn't get cut down, but some had the flash cone and or bayonet lug cut off and good luck finding parts.
those are the common varients that you will find, there are all sorts of other interesting but uncommon marks and varients.
oh and there is an entire sticky thread above with photos of enfields of all sorts.