I applied on 2th of August and they answered me very quickly via emails to every letter (if I had any concerns or questions etc.) and were very polite.
After applying online on the BA website I had to do an online assessment, which was much easier than I thought it would be (although the last questions needed some more time to think) and they invited me to the AD. As I'm not living in the UK, I took some time to book plane tickets and think my trip through before choosing the day for my assessment.
When collecting my documents and needed papers I always contacted them whenever I had an issue with something or I wanted to ask some more information and they were very helpful and quick to answer me.
On the assessment day I arrived a few minutes past 7am, so when I stepped inside most of the people were already there and seconds later one lady came to gather us in front of the gates and told us what to do. We all got an event pass (didn't really understand what was that necessary for) and went to the reception, where we all needed to fill some forms about tattoos and pre-booked holidays. When done we gave our documents and copies of them to the reception and first ones to finish were already called for the height check (also tattoo check if you had any) where we needed to show if our reach was long enough and if we could fit to fasten the seatbelt. Then we went to the waiting area and waited everyone to go through this step. Then we had a presentation about the company, typical roster, the advantages of becoming a member of BA and so on. After that we waited some time and were individually called for the role-play (or group exercise).
At the role-play there was a sheet where was 2 tasks. The first one was to read the text clearly and slowly (while standing up) and the second task was to use the same text as an information and remember it (you have 2 minutes to familiarise yourself with the text) and then the lady who's with you gives another sheet with connecting flight times and available seats and acts as a customer who missed his Manchester flight because of the delay of the first flight and is upset and wants the best solution you can offer her. TIP: read the info on the first sheet very properly and remember it!! (the lady acts very stubborn and wants to have a lot more than you are able to offer him).
It's about 20-30min waiting time again (there's A LOT of waiting time through the day) and then you are called to a group exercise (6 people) where you have a budget of £10 000 and you have a delayed flight with no equiptment and each one has a sheet that has different things with prices and quantities for every class (economy, business, first) and you have to supply the flight within the budget, thinking of everyone's needs (especially individual needs, ex. dietary/vegeterian), the flight time(our was 8hr so a pretty long flight to supply) and you have a certain time to do it (between 15-20 minutes). After you've finished this you have to wait for everyone else to finish their tasks and then you hear if you were succesful or not. If yes, then there is 2:1 interview that lasts about 20 minutes and that is the time they get to know you more are ask you questions about your life, why BA etc. They inform you about the interview results in 10-14 days (although it's usually much quicker).
Hope everyone enjoy the assessment day and be confident, communicate and SMILE a lot, the people there are very kind and friendly :)!