FIRST-HAND CAR RENTAL REVIEW · LONDON HEATHROW TERMINAL 5

My SIXT Heathrow Terminal 5 rental experience: a £764 booking and a £2,982 final bill

By Brandon Raynor · Published 29 September 2026

I booked a SIXT SUV category whose confirmation showed five seats and room for four bags. At the Heathrow counter, I was told it would not accommodate my family and luggage. I felt pressured to upgrade, and the final rental total was £2,217.92 above my original prepayment.

What I booked with SIXT

Months before our trip, I booked a “Fullsize Elite SUV — Audi Q3 or similar” for pickup at London Heathrow Terminal 5 on 8 September 2026. My booking confirmation stated five seats and capacity for four bags. I prepaid £764.39. We were travelling as a family of four with luggage, so the stated capacity mattered to my choice.

I understand that “or similar” does not promise a particular make or model. My concern is whether the vehicle category offered at collection matched the passenger and luggage capacity conveyed during booking.

What happened at the Heathrow counter

At the SIXT desk, the agent told me the category I had booked would not fit us and our bags. An upgrade to a Mercedes GLE was presented as the practical solution. The interaction felt pressured to me, especially after I had booked in advance based on the stated capacity. The larger vehicle only just accommodated our baggage.

I was told the upgrade was being offered at a 50% discount. SIXT later described the upgrade rate as £117.50 per day, which it said was half its standard rate. I want a clear itemised calculation showing the original rate, the claimed discount, other charges, and how they produced the final total.

Collection and the final bill

After the counter discussion, we were directed to the car park. I found the collection process confusing: nobody was available where I expected to check in, and I sought help from someone working for another rental company to leave the garage.

The final rental total was £2,982.31, compared with the £764.39 I had prepaid. I understand that I signed the rental paperwork, but I felt under pressure at the counter because I needed a suitable car for the trip. The size of the difference is central to my complaint.

My attempts to resolve it

I contacted SIXT by phone and email. I found the staff responses unhelpful and did not receive specific answers to my questions about the capacity claim and upgrade cost. A manager offered £329.94 as a goodwill adjustment, which I declined because it did not address my underlying concern.

There is also a separate scratch damage claim, which I dispute. I want that claim assessed on its own evidence, independently of the booking and upgrade issue.

After my experience, I read another customer’s public review describing a similar sequence: a car booked for a group and luggage, a statement at the counter that it would not fit, an upgrade framed as a deal, and a bill higher than expected. I cannot verify that person’s account, but it made me ask whether SIXT has examined complaints of this kind at Heathrow Terminal 5.

What I want SIXT to address

I want SIXT to explain what “four bags” meant for the booked SUV category, why I was told it could not accommodate us at collection, and how the promised 50% discount and £2,982.31 final total were calculated. I also want the evidence supporting the separate damage claim.

I have submitted a complaint to the UK Advertising Standards Authority about the online capacity claim. Submission does not mean the regulator has made any finding. I am pursuing my individual charge and damage disputes separately.

My advice to families booking a rental car is to check what the advertised bag capacity means and ask for an itemised price before accepting an upgrade. My experience left me deeply disappointed with SIXT Heathrow Terminal 5.