Join as Second Officer with full flight pay.
Any previous line training done at other companies means nothing. You will undergo full training but will be expected to be at line check standard by around 28 sectors as you will be trained under 'Operator Conversion Course'. (Minimum sectors a cadet will complete before line check is 68).
Most new joiners are now getting choice of base but there can be restrictions due to the requirements of the company. Also some bases are relatively small and sort after e.g GRO so seniority comes into efffect then.
Hope this helps.