Our booking engine at tickets.railforums.co.uk (powered by TrainSplit) helps support the running of the forum with every ticket purchase! Find out more and ask any questions/give us feedback in this thread!
Are the 'Budget' buses you refer to the blue and red Avis Budget minibuses? If so, they are directly operated by the company who have their own operator's licence.
Purple and white does indeed sound like the former Menzies fleet, that transferred with the contracts last year to Transdev Airport Services. It was expected that they’d all be replaced, although I suspect the timescale for that has probably slipped as a result of the pandemic.