https://www.caa.co.uk/Passengers/Resolving-travel-problems/Delays-cancellations/Your-rights/Your-rights-when-you-are-bumped-from-a-flight/

If you are bumped without your agreement, you are entitled to compensation, as long as you checked-in for your flight on time.

The level of compensation depends on the length of your flight and the timings of the alternative flight you are offered:

** For short-haul flights that cover less than 1,500km: ** * If the delay is less than two hours, you can claim €125 * If the delay is more than two hours, you can claim €250

For medium-haul flights that cover 1,500km – 3,500km, or flights within the EU of more than 1,500km:

• If the delay is less than three hours, you can claim €200
• If the delay is more than three hours, you can claim €400

For long-haul flights that cover more than 3,500km:

• If the delay is less than four hours, you can claim €300
• If the delay is more than four hours, you can claim €600