I have done levels 1-4 CSS.
For me levels 1+ 2, back to back take some beating.
This summer I did a S.P.O.R.T.S day with ESS at Croft - is this the post you were refering to earlier?
If so, it's a hybrid between a track day and a race school / day-ish.
Thus I have only pure tuition via the CSS and whilst the ESS did have some unusual features, I'm not sure I am the man to tell you one is better than the other.
Hope this helps.
Tim
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