Indicator stuck 'on'

I hate to say it but I told them so

 

I think it's interesting that no parts per million are listed....if looks like a smoke test and less stringent.

 

From GOV.UK website concerning the MOT and emission testing:

Most vehicles have their exhaust emissions tested as part of the MOT. Usually, they’re tested using a meter. Petrol vehicles used before August 1975 and diesel vehicles used before January 1980 are tested by sight.
https://www.gov.uk/emissions-testing

From 1/8/75 and before 1/8/86 emissions should be tested during the MOT, limits are:
Carbon monoxide (CO) 4.5% vol
Hydrocarbon (HC) 0.12% vol (1200ppm)

 

Your N reg bus only needs a visual test.

 

^this. Visual test is an easy pass (assuming you can still see across the workshop afterwards), figures for post 75 not onerous, even with a stock Solex.