Someone's already mentioned Johnson's who were the first firm that came to mind. MASS Engineering - if they're still going - operated a large fleet of deathtrap Titans certainly a few years ago - although whether they are still on the road, or whether they have all been given prohibition notices by now, is another matter.
The MASS (BrightBus) fleet now consists mainly of ex-Hong Kong buses of various ages, and a mix of Optare Spectras and ex-First Glasgow tri-axle East Lancs Nordics. The Titans have been gone for a few years.