Any question answered...

Excuse the long post - I have a DIY problem that is severely confounding me.

I intend to create a wall-hanging area for three bikes. This will be on an internal wall dividing the two reception rooms in my house. This is a solid, brick wall. I have a metal kick plate to attach to the wall for the lower wheels to rest against, and a same-sized bit of hardboard to attach above it. This will have three hooks that are drilled into the wall, though the hardboard.

Now to the issue:

I have a Stanley stud/cable detector which, completely unexpectedly, is going crazy all over the wall, suggesting that there are live wires behind it. There are no power points on this wall and the area where the bikes will be hung is away from the light switch.

After having an electrician over to hang some ceiling lights, I tested the wall after isolating the downstairs ceiling circuit and, lo and behold, the detector wasn't signalling live while the circuit is off, suggesting that there are lighting cables behind the wall - the electrician suggested that perhaps there were wall lights there in the past and the cabling has been left behind.

His suggestion was to leave the circuit on and go for it. If I hit a cable, it will trip out and not kill me (I hope he's right about that) and I will at least know precisely where the problem is, as opposed to turning off the circuit, drilling and then hoping it works when I turn it back on. Or maybe it will electrify the hooks and electrocute me. LOL.

I suppose my question is therefore whether there is a supremely accurate way to know what is behind the wall and where, so that I can avoid hitting any cables. Or is there another way to go about the whole thing?