I am asking your advice on this matter although it doesn't regard directly business case preparation, aplogies for that.

In June I have attended a final round for a consulting boutique in London. The HR confirmed via email that my logistic expenses (taxi, flights and one meal) would have been covered after the interview day.

Following the final round, that I did not pass, I sent the form with attacched all the recepies concerning the trip. Thereafter, I never got any reply from the HRs. I tryed to email politely multiple times waiting weeks in between until today.

Now it's the end of August, 2 months have passed, still no reply at all.
My quesiton is the following: what should I do? Have you ever been in a similar circumstance? Legally, considering the firm is in London, UK, what could I do?
The debt amounts to around 400€.

Thank you!

(edited)