31, Construction Project Manager, looking to enter finance. First Steps ? What A Levels to Study ? What Degree to take ? Pro's/Con's of my age ?

Good Morning, 

Quick Version:

31 Year Old Project Manager, wants to enter the finance industry, not sure what subject to study in university, not sure of the challenges he will face, seeking advice on how to overcome said challenges, the timeframe required and what the best educational and employment path would be.

Detailed Version:

A brief background to add context to my question:

Background

I am a 31 year old Construction Project Manager, born in London. I graduated secondary school (High School). I then entered the work force (Construction Industry) immediately, as further education was nor encouraged or plausible at 16 (mainly due to my family's lack of funds + the immediate need to provide enough money for the basic necessity's) *cue violin. So, I took a job as a labourer at a local construction site, cleaning, sweeping and carrying materials around.

Career to date

Over the last 15 years, from scratch, despite having very little passion for my industry I have worked and progressed through the ranks from a Labourer to PM level. However, throughout this period of time, I have and had always had a nagging feeling that I should have pursued a career in finance. In addition, despite the perceived "good earnings, seniority and authority" my role has gained me within my industry, I am incredibly dissatisfied with the apparent glass ceiling of earnings (£85,000 - £100,000 appears to be very close to the top of my field in the UK).

Why Change Now ?

Along with the lack of progress, interest or desire I have to continue working the next 35 years of my life in this industry. I want nothing more than to work in finance. Deep down, I always have. However a strange case of golden handcuffs/ "you have a good thing going here why quit and start at the bottom elsewhere" has for a long time prevented me from pursuing the study required. No more.

Life Commitments

I think it is important to mention at this point, that I am single, have no children, no major financial obligations like a mortgage etc. As such, outside of my 9-5 I have complete control of my time and finances to dedicate towards study.

Conclusion, Question.

As a result, I have decided to re-educate my self, attend an online school and obtain my A-Levels (1, 13 Months) and proceed to a university to pursue a finance/business/economic degree and obtain an entry level position within the finance/banking industry. I am aware I would initially likley have to take a huge paycut, and that this endeavour could easily take 8-10+ years to even achieve an entry level position. I am fine with this and willing to do whatever is required. Ideally within investment banking/trading however I feel somewhat naive and un-informed to make such general assumptions/aspirations about your industry and would appreciate advice on:

• What are the best A Levels Subjects, and subsequent University Degree to make me appealing to a bank and open up job opportunities. 
• Challenges I will face due to my age. (31 Today - 4-7 years of study I will be 35-38 When I eventually apply for positions. 
• Can someone at this age obtain an apprenticeship ? or take a very low level job like mailroom within a bank and work upwards ?
• Any advantages I have due to my age and proven track record in another industry.
• A rough time frame of progress.
• A rough idea of compensation once within the industry.

The impact of having top grades achieved online/not at a top university.

Is it actually possible to get into a top university at 31.

If you have read this far, I am aware this is a very long winded question and I'm very appreciative of your time and look forward to hearing your opinions and feedback, this goal really means a lot to me and any advice, harsh criticism, words of wisdom is welcome and appreciated. 

Thanks, Chris.