Southend sounds like a good plan. It may be worth checking out the availability of IR training slots, the last thing you want to be doing is wasting time holding outside controlled airspace in an expensive twin! I would certainly make a start in obtaining your PPL then see where it goes from there.
Some airlines tend to go the integrated providers as they have agreements in place in order for them to be able to get a constant stream of a known quantity of pilot at a very cost effective price. It’s got nothing to do with ability, all IMHO of course and I have no desire to get drawn into a mod/int debate here, that has been very well documented on these forums.
Decoding a METAR and nailing an NDB approach to the degree is all fine and well but remember that an airliner is a multi-crew operation; any selection process will include an interview where the interviewer will be assessing you against several competencies most of which are non-technical. A few examples are teamwork, overcoming hurdles and taking the lead. In an industry where commercial sensitivity is at an all time high they will be asking if you fully understand the role of a pilot and the commercial pressures that one can face in the role. For the technical side, some airlines consider the possession of a license enough whilst others may want to see evidence of flying ability in a simulator assessment, however in such assessment non-technical skills (CRM) will almost certainly be assessed alongside.
Best of luck