I wouldn't be too hung up on using linear bar for something like this. I'd personally opt for some bright finish bar combined with suitable metal bushings, as I suspect the loads may not suit linear bearings that well, and a few thou float would probably be beneficial to helping things align.
.
Eddy, I think most people on here have enough sense to identify real risks.
The type of machine that the HSE guide you posted a link to is aimed at, are automatic cycle machines, where you set it running, and it runs through the entire operation continually with no user interaction, which rightly should be protected by various guards/interlocks.
The type of machine discussed here stops as soon as you let go of the lever, so the only real risk is from you putting your limbs where you shouldn't. (well there are other risks, but they should be minimised provided the machine is designed correctly)