Regarding e-stop use in the UK, (and Europe), there is no legal requirement for the laser manufacturer to supply an e-stop with the laser projector. Although it is good practice to, and invariably e-stops are required as part the installers/operators obligations.
What the laser supplier must do however is for all Class 3B and Class 4 laser projectors, supply the unit with an interlock connector. The requirement is that the pins must be connected together to enable light output.
The other important requirement of the laser supplier is that any Class 4 lasers must also have a power supply reset feature, meaning that an action has to be taken by the operator to enable the laser projector in the case of first turning on, a power loss or interlock break, before the laser is able to emit light.
The better laser suppliers do implement this feature as is required by the EN 60825-1:2007 and later standards, which made it a legal requirement for CE purposes since 2009. But there are still a large number of laser projection devices being supplied or made in-house that fail to meet this CE requirement. If your supplier has sold you kit without this safety feature, contact them and demand that they do. Also, they are not allowed to list it as an optional (chargeable) extra either. For that would be like a car manufacturer selling a vehicle as standard without seat belts, and having them listed as an optional chargeable extra.
Stanwax’s PCBs are a quick and low cost way of adding the feature yourself to a projector that you have self built. I put some details on it on this link.
http://www.lvroptical.com/blog_PushTheButton.htm
BTW - there is NO requirement in the UK or Europe for the supplier to have a delayed start feature on the laser. This in not in the safety standard.
Ultimately, the better laser systems supply a remote that acts as an e-stop and also provides the power supply reset function as a separate switch.
Having the e-stop cut the mains power should really be avoided for a number of good reasons.
Hope this helps.
James