First I'd try to find a similar Enfield locally, or hook up with someone local via surplusrifles.com or enfield-rifles.com, and do a critical eyeball inspection of the locking lug cuts in my receiver. If they're smeared or buggered by comparison, I'd demote the action to "wall hanger."
If the recesses look reasonably similar to the other rifle, I'd strip the action down as far as it would go, then find a local engine rebuiilder who has a Magnaflux rig. I used to pay $10 for a local shop to check stuff for me.
In practice, a gunsmith isn't going to be able to do any better, and he probably doesn't have a Magnaflux rig, so he'd try to see any cracks by eye. If your bolt is badly damaged, checking the headspace wouldn't tell him anything useful.
If the rifle passes the visual and Magnaflux checks, buy another bolt and move on from their. Be aware that headspacing on an SMLE can be somewhat controversial...