The Isle of Man was covered in Programme 3 of Series 3. Given that Programme 6 from that series is being shown on BBC2 tonight, I'm surprised it wasn't shown 3 weeks ago. But looking at the schedules for that day shows that 'The Classroom Experiment" was showing at that time.
The BBC seems to be showing the 'Coast' programmes simply as 'fillers' in the schedules, rather than with any great deal of planning. (The repeats currently being shown on Blighty are from Series 1, 2 and 4. They don't seem to have bought the rights to Series 3).
If you're desperate to see the Isle of Man programme, it's called "Southport to Whitehaven"
http://www.bbc.co.uk/...port_whitehaven.shtml
You can watch online for £1.19
http://www.seesaw.com...uthport-to-Whitehaven
or buy the entire series on DVD for £7.49:
http://tinyurl.com/36p2kjq
Chris