K. In answer to your question, those locks probably wont come apart anyway
well, not without some drilling/cutting and possible destruction
Some locks are easier than others just because of the key bitting,
I can't imagine halfords own to be particularily high security but you never know.
You might want to try your hand at a yale 5 pin door lock, like you find on
most front doors, the proper brand yales usually have a couple of security
pins in them. The cheaper ERA ones don't in my experience but they are good practice.
If you want to stick with padlocks, Abus, Yale and Chubb are decent ones
to look out for. Also look at the keys. The ones with a good difference in the
high/low bitting will be more of a challenge.
Hope that helps.
