Hey Michael,
here, let me address a couple of your concerns ...
First of all, obviously you'll get a lot of questions about how much time you can spend it ports. Specifically, did you have time to act almost as a tourist in some ports? Where you able to properly explore the areas you were in, or is it really almost impossible to actually see much of the places that you go?
Do not believe all those storied about hard work and 14 hrs day ... dependable on position, you will have more or less time in ports, but you WILL have time off, and you WILL feel and be a tourist, with the great advantage of being paid for your time onboard. You have mentioned a bartenders job, so let me tell you that it is probably the best position you could get. Lots of fan in bars and very decent money.
The second question is about job competition. Clearly a job on a cruise liner is a dream job for many people, so is there a lot of competition for jobs? How would cruise liners pick who to employ out of a list of non-skilled applicants? Would it be better to train say as a bartender before applying, and therefore have a better chance of entry?
They will not take you as non-skilled for bartender's job, period.
You will have to have the knowledge of mixing drinks, cocktails, wines, wiskeys ...
I suggest you get at leat a short course before applying for position.
Feel free to inflate your CV with imagenary experiance, they simply do not bother to check with your alleged previous employer(s). Use your imagination, but have someone to answer the call you mention as a reference, just in case.
The third question is about the holiday time. You said that you get a couple of weeks of unpaid vacation for a 6 month contract. Would this vacation have to be on the ship? Or could it be taken while at a port, hence using the vacation time to explore the area? (Kind of linking into first question there) Would you be able to fly home and back for that vacation?
Your vacation can not be on ship, unless you pay for it. Your room gets occupied by other guy, and upon your return, you get another room. Never met a guy who wanted to stay on ship during vacation. In most cases, the company will fly you home and back to the ship, at their expense.
My next question is about personal space; I have this vision that on this huge cruise ship I'd be able to find a special personal place that most people wouldn't know about, and therefore be able to spend some personal time there. Would you think that things like that would occur?
Here lays my only concern for you. Among 3-4.000 passengers and 1.200 crewmembers, it is close to impossible to isolate yourself. First of all, you share your cabin/room with a roomate, and the only recreation area for crewmembers onboard is crew bar. You have internet room and gym, but that is it. You can not hide.
As a bartender though, you would be often free during daytime, and that is when the crew bar is empty.
You can reed a book or have a coffee, and nobody will bother you.
My final question is surrounding computer and internet access on-board.
Would workers be permitted to bring laptops with them?
And would the internet on the ships generally be available while sailing?
You are welcome to bring your laptop, but most crewmembers buy them in tax free ports for lesser price.
Internet IS generaly available while sailing, $20 for 200 minutes. I recommend to use it in ports.