I really wish I'd seen these reviews before I made my booking.
I booked at the Hilton Syon Park for the 14th July 2018. When I arrived at the hotel (after a 5 hour drive in sweltering heat), they had no knowledge of my booking. I had the confirmation number and print out but they still couldn't find anything on the system.
After the hotel had spoken to gta and Elvoline, it seems that Elvoline had 'booked' a room without actually confirming this with the hotel. They did offer to put us in another hotel in central London (not where we wanted to be as we were attending a concert at Twickenham Stadium). And by the time we would have got to said hotel our concert would have already started.
They have offered a refund, but quite frankly that doesn't cut it. My husband and I couldn't have a drink and enjoy ourselves as we had to share another 5 hour car journey back home!