TAG manage aircraft owned by individuals or organisations. Most aircraft are on TAG's AOC and therefore available for charter. The ratio of private/public transport flying varies greatly from one aircraft to the next.
The initial interview would probably be with MD and/or CP and/or CTC and/or HR person. Probably followed by second interview with aircraft owner. Do not expect an airline style group exercise, psychometric test, etc. I do not think sim assessment is normally involved.
Salary is negotiable. They use a 'per diem' system (don't know how much), private medical, money-purchase pension.
DO NOT EXPECT AIRLINE STYLE ROSTERING. The nature of this type of operation precludes set-in-stone work patterns. Of course the public transport flying is subject to the exisiting Flight Time Limitations.
Appears to have very low turnover of pilots - probably a positive indicator of terms and conditions, morale and job security.
Clearly a very well-funded organisation that's been around for a while.
Importantly, if you 'get' a good owner and a good crew (bearing in mind you will be working with the same, small number of people) you will get much more out of the job than if you 'get' a crap owner (overly demanding, no understanding of crew limits [fatigue], miserly, know-it-all, always late, disorganised). This factor greatly influences the quality of your job and if you get stuck with a crap owner and crew you don't like then it could be unpleasant.
Good luck and safe flying!