the Guaranteed vehicle availability is here in the PC T&Cs
*Guaranteed vehicle availability
Guaranteed vehicle availability is available with a minimum 48 hour advanced reservation. Vehicle availability is offered at participating Hertz locations in the U.S., Canada, Namibia, South Africa and participating airport locations in Europe (Brussels, Berlin, Dusseldorf, Frankfurt, Hamburg, Munich, Stuttgart, Helsinki, Oslo, Rovaniemi, Turku, Paris Orly, Paris Charles de Gaulle, Marseille, Nice, Toulouse, Lyon, Bordeaux, Athens, London Heathrow, London Gatwick, Manchester, Edinburgh, Birmingham, Dublin, Milan Linate, Milan Malpensa, Rome Fiumicino, Amsterdam, Vienna, Lisbon, Madrid, Barcelona, Stockholm, Goteborg, Geneva and Zurich). Guaranteed availability only applies to Economy through Full-size 4-Door cars.
https://www.hertz.co.uk/rentacar/eme...esidentsCircle