Is it the amount of transactions through the credit card or the magnitude of the transactions that counts?
My undertanding is that any application or use of credit leaves a footprint on your credit score. So if you apply for and refused a loan, it will have a negative effect. I also hear that any application for a "pay day" loan (1000s of % apr) has a negative effect.
am I right in saying the bank will not give out any loan if you have anything to pay off on a credit card?
Not necessarily. When offering you a loan, the bank looks at two things, firstly your credit score which allows them to assess whether or not you are a risk to give an unsecured loan to, and then they look at their responsible lending criteria. This means that in their eyes you are able to afford to repay the loan, otherwise it would be irresponsible to give you a loan where you cannot afford the monthly repayment and still afford to live. Let say their criteria is that you need £900 a month just to live, you have credit card debt with monthly repayments at £100, and you earn say £1200, they would only offer you a loan that fitted that spare £200 that they have assessed you have. This would then dictate the amount of money you could borrow, and the term of the loan.
And, what if you have a job offer but need to fund a TR? Would that increase the amount you could borrow (unsecured I mean)?
This is where the bank's responsible lending criteria gets very annoying. Generally they assess the amount you can borrow based on your last three months of earnings, to assess whether you can afford repayments. Obviously in the case of a paid type rating you would hope that it would lead to an almost immediate increase in earnings (say stepping up from a flight instructor earning £15k a year to an airline earning £30k a year). The banks generally don't see it this way, and only look at your last three months, then tell you that you can't afford the loan, or make you spread it over 5 years instead of three which lowers the monthly payments but increases the interest paid.