1st class you're absolutely right;although speedmarque was probably just trying to motivate, all BA crew will welcome you with open arms and WILL NOT expect you to know where everything is & how to complete the service on any given flight - certainly you will be expected to be eager and willing to learn - the rest is simply experience and ASK, ASK, ASK. Many shorthaul crew have fairly little seniority anyway - a large number joined in the last 3 years, which is very recent by BA standards!
You won't be the only new people around either...many longhaul crew will be transferring over to shorthaul and believe me, they have don't have much experience of shorthaul aircraft, galleys or 30 minute Manchester flights, so you will not be on your own!