Different levels of IAPT services?

[BursarsFrogs]

I hear there are four tiers of services, but what does this mean in practice? I was recently assessed, and told I'd probably receive "tier 4", but have apparently been put on a waiting list for "tier 3" services. I assume it will be talking therapy of one kind or another, but what exactly is the difference? Do you move from one tier to the next, if you fail to improve?

I know that initially I was given level 2 which was a short course of CBT (six sessions, although they stretched mine to 8 in the end) with a PWP - psychological wellbeing practicioner, so someone who had training just for that level. Then they put me up to level 3 which is 12 weeks with a CBT therapist, someone with a higher level training. I was given the impression that level 4 was beyond what the IAPT service does. I think level 1 is self-directed online/self-management stuff.

Thanks. I really hope I'll something more than 12 sessions of CBT (been there, done that), but I guess I'll have to take what I get.