Re Which Career:
1. Ask yourself if money were no object which would you do?
Which do you enjoy more? Which do you get a kick out of?
Which will challenge you? Which has greater development for you?
This answer is important because you will be working in that career area for the next 10-30 years, you need to be happy doing your day job.
These answers only YOU know.
2. IF and I say IF your agenda is eventually to end up self employed/have your own business, then looking at each objectively, here's what I think.
As a warehouse operative, stores and purchasing, there is a very low chance of being self employed/own business.
As a supply chain specialist, yes there are consultants out there but I wouldn't say there are more than 50 of them in the country.
Yes there are a good number of permanent jobs in companies for supply chain but as a self employed consultant, not a huge amount.
As a payroll specialist, there are many jobs working part time/use a self employed person that run the payroll for companies. However most payroll people work full time as payroll has become more and more computerised and easier to run with the likes of sage micropay etc, so it doesn't lend itself to being a highly demanded specialist consultancy service. I run my own small companies payroll, it ain't complicated.
As an accountant or even a tax specialist, you have a good chance to becoming self employed/own business. (IF as said in the other post that is something you really want).
The reason being is that EVERY company that exists needs accountancy services. Annual accounts, VAT, payroll, etc all need to be done.
There will always be jobs / self employment work for accounants/tax specialists. If you are training in an accountancy firm directly, the money can be low, however once trained the money is very good.
My advice is that if you are interested in the accountancy/tax route, I would take that option.
As regards which course, find somebody who is an accountant or call up an accountants firm just to talk to somebody who knows which course might suit better.
At the end of the day, this is my oppinion, it all boils down to what you want.