As MC says, Albie Fox is a damn good place to start.
Custom jobs no problem.
He's always delivered on time - or early.
Multiple colours/personalisation also a doddle here.
Setup prices may well be low as he already has most capbadges in stock.
He might be a little more expensive than other firms, Hargreaves for example, but this is more than made up for by the quality of the embroidery and shirts.
He decided a long time back not to sell cheap, but go for good kit.
All the ones I've had from him are still in excellent shape, no fading stretching or sagging - some are over ten years old.
The other reason I use this firm is that he's an ex-soldier & it sort of keeps everything 'in-house' as it were.