I've signed petitions on the No. 10 website before, and as far as I can see it did little good.
In the case of the road pricing one, the politicians dismissed it saying either that something had to be done to reduce road use or that they were elected to take difficult decisions and we live in a 'representative democracy' and don't hold plebiscites... The reply to the petition with well over 1million signatures from Tony Blair was, in my opinion, a master class in how to say nothing in as many words as you can whist appearing to be very concerned.
In some cases, where enough sign but not enough to make the news, the people who monitor the No. 10 petition system send some bland response usually saying something like "this has been passed to the relevant ministry or minister for consideration". Which I read as meaning that nothing will happen.
In the case of others they just claim that not enough people signed and ignore them as well.
The CE marks? Well, although there are EU regs, it appears that you only have to say that your equipment meets them, you don't actually have to prove it unless there's a likelihood of risk to life or limb... Basically, from what I can make out from people who have looked into getting a CE mark, if you self certify you take the risk that someone gets hurt and sues. The CE non-conformity then pales into insignificance against damages that could be awarded against you. If there's little risk of that then the costs of being prosecuted in the EU courts are low, as the allegation that you 'think' something isn't compliant is not acceptable to the EU courts, you would need to prove that it doesn't comply, and so you, not the manufacturers, would have to get the tests done at your own expense and that could be a lot to put up front and risk not winning the action in the end as well...
I could be wrong, but that seems to be the response from people involved in manufacturing who have self certified.
de Dave (G0DJA)