The cab companies/cabbies are mostly scared of one main thing. They invested a massive amount of money to by their exploitation licence. The main regulation that they are concerned with is this quota. The rest of the regulations are generally nonsense or exist to prevent gross fraud. If Uber is given the green light these exploitation licences become valueless. In some municipalities these licences have traditionally sold for the million dollar zone. There are even banks that specialized in loaning money for the this market. Thus the cabbies will be on the hook for a licence that is worthless while competing on price with an Uber driver who wasn't stupid enough to put that yoke around his neck. Then the pricing regulation was there to largely protect their ability to pay off that loan. Thus there are two groups here, one is those who have paid off the loan who love the huge amount of money that comes from exploiting Londoners with this monopoly, and the other group are those who must have that monopoly pricing in order to pay the loan. Then when the cabbie retires they could sell the licence for a fortune.
But I don't ever remember signing an agreement saying that cabbies could rape my wallet.
Their PR arguments also hold no water. Let's assume that all their arguments about safety, quality, crime, and so on are all true. Why should we not have the choice anyway to pick who drives us? I am happy driving a friend to a location, they are happy to drive me, people drive themselves, yet somehow cabbies have twisted this into licensed uber drivers as being the best way to get yourself killed. So the regulations that largely exist for all drivers such as not being drunk, having insurance, having a safe car, having a licence, all make sense for normal drivers; so why don't they make sense for Uber drivers. Does the uber app somehow make them worse drivers?
But again; even if uber is terrible and dangerous, why should we be treated like infants and not allowed to make up our own minds? Also continuing with the uber is a death trap; then other companies could come along in a free market and offer safer drives. People would probably choose them instead. Free market. Just like all the other vendors in London who don't have quotas. Restaurants, lawyers, dentists, clothing stores. All of those businesses would probably love a quota eliminating new competition. But it wouldn't serve the public at all.
If you want to see a wonderful example of something that is this taken to its extreme: try and get something notarized in Italy. Something like 1,000 Euros. I think a Notary in Canada or the US will run you around $50.
But if this monopoly had never been set up and competition had always been allowed we would not be having this discussion and Uber would be having trouble making any headway in London, it would simply be one more competitor in a competitive market.