Hello Jon,
Obviously your (DIY?) call, but having a general distrust for garages of all ‘sizes’ isn’t really healthy.
Trust is always two way, and as you say you have to start somewhere, and simply asking around friends and acquaintances usually leads you towards making a good start.
May sound daft, but enquire about recommendations at local small car sales sites. These chaps remain in business by knowing where to get good work done at competitive rates - so always worth an ask. Now don’t tell us you you don’t really trust some of these as well! I’m sure you do.
Kind regards,
Gareth.