Hi Duncan - just remember reading a post on Mahem where some were saying that the quality had dropped. If you Google Humbrol paint quality it throws up a few comments.
Also complicated by Humbrol having to stop supply earlier this year and shops not being able to sell it as one of the chemicals, MEK, was banned on safety grounds, until the paints had been reformulated.
Don't know exactly where they are with that now and Humbrol is now under the HornbyAirfix banner. Would be good to hear from someone who has used the latest offerings.