It's a Mk III*. The .303 2.22 stamps are typical Brit proof marks required on any milsurp rifle that was sold through England. The 'ENGLAND' is an export stamp. The 'GR' means George Rex. As in King George V of England. Plus a swarm of assorted Brit proof and acceptance stamps. Broad arrows and crossed flags.
That front sight is aftermarket. You must check the headspace on sporterised Lee-Enfields.
This is a pretty good site for No. 1 Lee-Enfield stamps.
http://www.allaboutenfields.co.nz/history/markings/