I visited in October last year (also from the UK) with a group of friends. I'd say its 100% worth the trip! Zadra (my current #1 coaster) and Hyperion are the 2 standout coasters. Abyssus is a excellent new-gen Vekoma multi-launch. Plus the park has a huge number of family and kiddy creds.
My main advice would be to pre-book your transport to the park well in advance. The park is located in Zator which is about halfway between Krakow and Katowice, but it is in the middle of nowhere. We stayed in Krakow and did 2 days at the park. The park runs a daily coach between Krakow and the park but by the time we came to book it, seats for our second day had run out. Zator does have a train station so we assumed we'd be able to get a train, but the staff at Krakow's main station weren't overly helpful and we ended up taking a taxi. (Fortunately Poland is pretty cheap so it wasn't too bad after we split the cost between us). We took the coach on the first day, and it was far easier so I'd highly recommend doing that. You can book on their website (https://energylandia.pl/en/dojazd/autobus/)
Happy to answer any other questions :)