From their website,
"ANSWER
I WANT TO CANCEL MY BOOKING, WILL I GET CHARGED?
If you wish to cancel your booking outside of 48 hours prior to arrival, there will be a £1.50 GBP (inclusive of UK VAT) Administration Fee per adult. However, if you wish to cancel your booking inside of 48 hours prior to arrival, then there will be a £5.00 GBP (inclusive of UK VAT) Administration Fee per adult."
As the booking was consequential to the cancellation, I believe they need not refund the whole amount.