Firstly the only direct flights are into Heathrow and they tend to be cheaper too. Eva air is good and mostly comes out best. No point having a car in London, congestion charge etc. for car hire start with moneysavingexspert.com where they'll also give you links to insure the excess (CDW) separately from the rip off the car hire companies charge. Yes it pays to book in advance too especially in peak summer time.
Good luck