For $225, I'd buy it if the bore and action are good. The Long Branch is GTG.
Most of the SMLEs and No4s had "generous" chambers, but .303 Brit headspaces on the rim, so don't compare a fired cartridge to an unfired one and panic. Headspace gauges are available from multiple online vendors, but few people shooting SMLEs seem to have ever check their headspace. Bolt heads come in 4 sizes to correct headspace issues; you don't have to pull the barrel or anything drastic like that.
Personally, I'd have to replace the forestock and handguards to return it to original configuration, so I'd haggle a bit on price. All 3 pieces plus the metal can be had for less than $100. If you can't find a Mk1 forestock, the Mk2 can be modified to fit pretty easily.
Parts List (*)