I certainly would not leave a job or plan building a career at Qantas UK.
Now 'cheaper' contracts have been introduced for Australian based crew its actually cheaper to have crew all based out of Australia than have a base in the UK.
As Qantas always wants to 'save a dollar' I doubt the base will be around too much longer.
Still if you haven't flown before Qantas UK will give you some fantastic experience for your resume.