I would like to report that Europcar has not gotten any better, and you should avoid them if you come to London. If you google "Europcar, London, congestion charge" you will find complaints on this issue going back many years.
I have lived in central London for thirty years, and rent cars fairly regularly. I recently rented two cars for overnight trips from Europcar at two separate offices - Euston and San Pancras. I was quite aware of the congestion charge, though I usually rent from inside the band, and never had problems; I had mis-assumed that these offices were also within the congestion charge area.
In BOTH cases, one month after rental, I was hit with the 101 pound fee for taking the cars into the congestion zone. Neither of the Europcar clerks told me that I would need to pay if I drove a few hundred yards into London.
I have been looking over many travel forums in which other customers have complained about this problem over the PAST THREE YEARS. You will note that almost every time someone complains, their complaints are inundated by trolls - making fun of these people for not reading their fine print. It's my opinion that many of these obnoxious souls are employed by Europcar, or some PR hack.
Europcar has NEVER in all these years simply informed their clients - who come to them from all over the world - that they are within a few hundred years of a 100 pound fine, which doesn't appear on their credit card for more than a month. This is ridiculous. DO NOT USE THIS COMPANY, or pay attention to the trolls who will undoubtedly reply to this post about how ridiculous I am for not reading all these adhesion documents.
Good luck. London is better than this. But Europcar is a bad company and, in my experience, will screw you out of every nickel. read more