EasyJet reimbursement shortfall

Docsaibal

My girlfriend and I were due to travel back from Milan to Gatwick and the flight was cancelled a few minutes before we were due to board due to diversion of the incoming flight from a lightning storm (therefore crew changeover could not take place). The ground staff simply asked us to make our own arrangements and left us stranded, hastily promising reimbursement for expenses if we kept all the receipts. 

We were literally retracing our steps back through security and towards the exit while I was frantically looking for flights back. Predictably, everything was booking fast and the priority was to get home rather than look at costs. We ended up booking the next available flight out which was on Sunday morning (our cancelled flight was for Friday night). We made our way to the Malpensa  airport hotel, decided to stay for a night and relocate to the Linate airport hotel where our new return was from, and kept all food, beverage and taxi receipts meticulously, being careful to keep expenses reasonable. 

Having submitted the claim, I have just had a reply saying they would offer reimbursement only for the ‘day of disruption’ as we had accepted a voucher/refund. This was despite the fact we took the first available EasyJet flight back which would keep us back in Milan for two more nights. My girlfriend who had booked the original travel was given the website option of refund/voucher or alternative flight. As EasyJet left us to our own devices there was only one option we could take, (and I had advised her to not ask for a voucher)

Here’s how much out of pocket we now are:

Meals and refreshments £267.53, offered £60;
Accommodation (2 nights) £372.89, offered £200;
Airport transfers £145.15, offered full amount.
Return flight £537.23, refund on original flight offered £464.60.

Total not honoured = £453.05.

What are our rights and what should we do?