You are fine to pack everything to one bag and check it in. Usually when traveling we are going with one big bag for 2 - 4 people and each with ~45L backpack we are taking to cabin with us.
You are ok to take harness, helmet, crabs and sling in to a cabin. You can even put a helmet on your head to save space. Safety first! Just attach it to a backpack and if RyanAir minion have problems with it put it on your head. Rope is sometimes stopped by security.. I am still not sure that danger it posses, but some particular security officers consider it to be a dangerous thing to carry in to a cabin.
Another thing you may consider is to buy new gear in a country of your destination. Ropes in Austria for example are generally 25% cheaper than in UK.
Post edited at 15:48