What do you think the best work to the continent is, regarding hours, pressure, money etc. Is it fridges, tilts etc. work for small operators or multi-nationals.
Yes and No to all of your suggestions 
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There are good and bad points to each combination.
Small hauliers can be good people to work for, treating there drivers like part of the family. Some are pleasant to you at the interview, making you feel welcome. As soon as you are on the books they treat you like a slave. Just the same as UK domestic companies.
With large companies, it often depends more on what the depot manager is like, or the particular TM who you are controlled by.
I worked for Murfitts, who used to have 400 wagons in Europe on any one day, plus their European drivers who were tipping and loading in the UK or having their time off at home. Some people who I have talked to couldn’t stand the company and left within weeks (sometimes days) of starting. I had two different TMs, who I got on well with and I enjoyed my time with the company.
The work, whether fridges, curtainsiders or box vans, is much the same as UK domestic work. Simply that it can take 3 or 4 days (legally) solid driving to get to your drop. When you get there the security person speaks a different language and the signs telling you where goods in or out are also in a different language.
The biggest difference, for me, is that over the water most of the people we deal with appreciate our efforts. We are treated with some respect (usualy) and instead of being greeted with, “What the [zb] do you want? Just park on the road, we’ll call you when we’re ready! No you can’t use our toilet, no you can’t use our canteen!”. The greeting is more along the lines of," Oh good, your here. Did you have a pleasant trip? Sorry, but there is another wagon in being tipped at the moment, would you mind waiting for 10 minutes? If you like, go into the office, you can help yourself to a coffee". Not everywhere obviously, but the majority of places.
So basically we can’t answer you question, it all depends on what type of work you prefer. Also which type of company you prefer to work for. There are plenty of threads about different companies, asking what a particular company is like to work for. Many of them get a good report from one person and an opposing opinion from someone else. Most of those threads are in the Professional Drivers Forum, some are in here. They might take some digging out. You could use the “search” button, at the top of every page. Put in the name of the company you want to know about, something will probably come up. If nothing does or its a bit old, try asking directly in a new thread. Someone will know something about them.