A quick note on fixing Ground Anchors. Make sure that you’re fixing it to a concrete slab rather than a sand / cement screed. Although, it is highly likely that [in the UK] a garage floor is a concrete slab it’s worth double checking.
Personally, I use a multi-layers security approach.
Externally, my ‘shed’ has low key reinforcements so not to attract obvious attention.
Internally, I have multiple types and size of locks. A sacraficial bike. Finanly, I have electronic alarms too.
Almax are a buy once item and are, for all intents and purposes, indestructable.
Ultimately, if someone wants YOUR bike(s) then they’ll get them. Therefore insurance is your ultimaate protection.