I'd be very grateful for advice on this.

My boss and his wife were travelling from LHR-JFK. I booked and paid for their tickets (since I organise the travel). They were ticketed in WTP. At T-24 they were unable to OLCI and kept trying throughout the following hours, but were unable to do it.

At LHR, checking in in plenty of time for the flight, they were downgraded to WT. I believe they were given a debit card preloaded with some cash but haven't had a chance to check the full details.

Two questions:
1. Who should pursue the EU compensation -- me (purchaser) or them (passenger)?
2. Thanks to the excellent EU compensation sticky thread (thank you for this), I am assuming that compensation is due (75% of the fare paid); I also assume that the airport compensation (if any) does not relieve BA of its liability under the EU compensation arrangements, but if I have misunderstood, I'd be grateful to be corrected.

Many thanks.