Economics vs Mathematics with Economics

I currently hold an offer to study Mathematics at UCL and was considering transferring to one of Economics or Mathematics with Economics.
I have some questions:
Is it possible to transfer from Math to Economics or Maths with Economics and if yes is it possible to transfer back? Please provide as much details as possible.
The Economics degree seems to have a large proportion of math or math-y modules, assuming I transfer to Mathematics with Economics, will I cover all the maths and statistics covered in Economics degree and how much of the economics in the Economics degree will I cover as a percentage, can you comment on this percentage?
What are the economics modules like in Mathematics with Economics degree?
If I am planning on working in something directly related to economics (eg. finance) is a straight Economics degree a significantly better way to go?
Many of the third year and second year economics modules are open to Mathematics with Economics students what does that indicate?
Which is harder and which have better prospects and why?

I have A-levels
maths A*
physics A*
Predicted:
f.maths A*
chemistry A*
Arabic A*
Any general comments is appreciated.

1) I'm sure the economics department would take you with your grades. Email them and see what they say.

2) Mathematics with economics = 75% maths, 25% economics. would be an economics minor so you'd still be doing a maths degree basically

3) Neither has better prospects - pick whichever you enjoy and think you'd do best in

4) Neither is harder or easier, depends where your strengths and weaknesses lie. Economics is more applicable and logical, but maths is theoretically rigorous.

5) An economics degree won't help you with a career in finance, they're two completely different things. There is very little overlap.

1) Thank you.
2) I am still unclear about I will cover all the maths and statistics covered in Economics degree in a Mathematics with Economics degree and about how much of the economics in the Economics degree will I cover as a percentage in the Mathematics with Economics and can you comment on this percentage?
Ellaborating my question more; The Economics degree includes in the first year 25% dedicated Math modules and 12.5% statistics, I am not sure about the other years, my question is will I cover all the maths and statistics covered in these Economics degree in a Mathematics with Economics degree? and ofcourse there are dedicated macroeconomics and microeconomics in the Economics course not sure about the percentage, how much of it will I cover in the Mathematics with Economics degree, Is econometric courses covered in Mathematics with Economics degree?
3) and 4) I didn't mean to be rude.
5) Wrong word, don't really know the difference, would be glad if you would like to offer your input, I meant banking and stuff and this word came to mind
Should I do any reading over the summer and again any comments are appreciated.

They refused to transfer me.

Unlucky. What are your options now?