I spent about three weeks solid preparing for mollymawk as I was at school some time age. It is do-able with preparation unless or without if you have not long finished maths/science GCSE/A'level.
Working memory test is what everyone finds most difficult.
Sim OK but also a couple of hours practice before is big help - Virtual Cambridge. Raw data departure, engine fail, NDB approach that sort of thing. Allowed to use the FPV.
Interview with HR, pilot and German psychologist who makes you feel at ease and then tries to get you agitated or angry - asks bizarre questions of which the answer is probably not that important but the way you handle them.
On line, interesting work, but very hard work. The roster is often a work of fantasy and subject to constant changes. Eat, sleep, fly mostly. They generally look after you ok and leave you pretty much alone to get on with the job. Others may see things differently to me - best of luck