I have a similar problem in that my garage is in a separate block, although only a little way from the house. You've seen some of what garage contains and I'll admit to being worried on occasion, despite the almost non-existent crime. I have wall anchors positioned so I can get a decent D-lock and cables through the frames and more exotic wheels. Unless the walls are pristine, these would only leave easily fillable and disguised holes when you had to move out.
I've also considered (but not bought) an alarm that will phone/text if it goes off. They're quite reasonable these days - example here.
https://www.ultrasecuredirect.com/w...attery-ultrapir-gsm-alarm-007-1150-p1167.html
I'm also a bit cautious about installing security that's out of keeping with the other garages. It screams valuables. One other thing - I've got a sacrificial crappy old bike that I leave unlocked so that, if a feef gets in, they'll see the locks and just grab the one thing that isn't.

I've also considered (but not bought) an alarm that will phone/text if it goes off. They're quite reasonable these days - example here.
https://www.ultrasecuredirect.com/w...attery-ultrapir-gsm-alarm-007-1150-p1167.html
I'm also a bit cautious about installing security that's out of keeping with the other garages. It screams valuables. One other thing - I've got a sacrificial crappy old bike that I leave unlocked so that, if a feef gets in, they'll see the locks and just grab the one thing that isn't.
It's a CITY Jay, not bloody Basingstoke! Don't make me report you to the committee.. I live in a relatively low crime provincial town, although bike thefts from garages are not unknown.
