There's also Wilks in Flies North, where Biggles also buys an airplane - and half Wilks's company, as far as I can tell - and happily takes on all kinds of gangsters in order to get Wilks out of trouble. But at that point Biggles basically just wanders around doing whatever he feels like anyway. Later-series Biggles doesn't usually go off the rails the way he does in Looks Back <3

Algy absolutely deserves a medal for putting up with everything in Looks Back, plus no doubt months of cranky recovering Biggles at the end (though we hope he can outsource that job to EvS and Marie...)