Career route progression.

One thing that Ellen Rogers taught me in her lecture at the university is that there is not one single route into a job role. She fell into fashion photography after meeting a stylist who was well connected and wanted to work with her.

So I think its safe to say that there are many different ways one might go about getting a job role in the industry but to be specific -

Assisting - If I were seeking a role in assisting a photographer I would email them and offer my services and then follow up the email a week later with a polite phone call. This is one of the best ways to secure an assisting role as photographers rarely advertise for them.
I would need previous experience in assisting if I were to assist established photographers but this can be gained from assisting less established photographers. I would need to have good communication and memory skills.

Freelance retouching - I would advertise myself as a retoucher and seek out freelance jobs.
Employed retouching - I would seek a job with an agency with a portfolio that was strong.
For both of these roles, photoshop knowledge is key. I'd need to be efficient and stick to deadlines and have good communication skills in order to give my client what they need. At this moment in time there are several companies and agencies taking on retouchers in London such as Twist Recruitment, Success Digital, Touch Digital. There are also many companies that are taking on in house retouchers at the moment such as ASOS, the online clothing brand and Footasylum, a shoe brand.

Freelance photography - I would need to perfect my self promotional package and market myself well in order to shoot enough to pay the bills
Employed photography - I would seek and apply for jobs with agencies and companies.
Both of these jobs can also stem from assisting and building up a client base. Again with these roles I would need communication skills in order to deliver and time management to stick to deadlines.
There are several employed in house photographer jobs being advertised in London at this moment in time. Some of those include photographing stock for Selfridges and Amazon.co.uk