A few years back I rented a car in Scotland through Europcar and they tried to gauge me on only accepting their insurance at $15 per day. (it was 200% over what my rental amount was) and was able to switch to Enterprise which allowed my credit card CDW (collision damage waiver insurance).

Last year I flew to Ireland and I booked through Budget and they tried to charge me a bunch of "road" fees and insurance waiving "administrative" fees.

With that data in mind, In April of 2020 I'm flying to London Heathrow and though I won't be driving into London, I'd like to know if there are certain rental car companies I should avoid that will require additional fees and what is considering normal and what is considered a load of rubbish?

Any advice on who to avoid for crap fees and what fees I should truly expect would helpful.