The wandering zero is mainly a myth. There can be phenomena with almost any rifle, where the barrel isn't floated properly, bands over-tightened, etc., but most JC owners I've talked to say it shoots just fine.
As for recoil, it's much more pleasant than an 8mm Yugo.
I really enjoy shooting the JC, and I think it'll be one of your all-time favorites. The .303 is an awesome round, and the No.5 Mk.1 is well-designed to use it.
The main things to look for before shooting:
1) Bore obstructions (duh).
2) bolt and receiver serial numbers matching (an indicator that head space is good.)
3) Cracks/damage to the chamber, bolt, and barrel.
If these check out OK, she should be all set to go. Happy shootin'.