In reply to oceannash909:
As already stated, the decision lies with the individual security officer. It all depends on what level of risk you are prepared to tolerate.
UK Airport security is under extreme pressure currently and this pressure will magnify personal behaviours making officers either more likely to ignore or more likely to challenge and/or confiscate.
For risk free travel put all climbing gear in the hold. I recently travelled hand luggage only to Spain, carrying just personal gear, harness, shoes, gri gri. The gri gri was challenged on return flight.
You are flying to alicante where there is a large decathlon, any losses can be replaced there if you are unfortunate.
In the good old days when the pound was strong against the euro, it arguably made sense to buy gear at your destination, using both the exchange rate and saving on the outbound hold bag to subsidise your gear shopping. A good strategy when/if those days return.