I applied to Economics at Manchester for L100 BA Econ and i'm probably going to accept the offer (maybe St Andrews). I've recently been in touch with them about the difference between the BEconSc (L101) and the BA Econ (L100) due to the BSc being better than the BA debate. The difference is that the BA Econ is run through the Economics and Social Studies department - hence the name. All this means is that application to this degree doesn't tie you to it. You are free to move around within the department, including subjects such as Finance, Accounting, Politics etc. You have to choose your specialist area in the second year. If you follow Economics then you will get a BA Econ in straight Economics. The BEconSc is run only through the Economics department and is aimed at people that already know they want to specialise and only focuses on core modules. Your choice within the degree and its flexibility is fairly limited. I think that is why the BA Econ is more popular - people who are unsure where their interests fall are attracted to it. I was because i am considering specialising in Financial Economics to go into investment banking - the BA Econ gives me this option.
With regards to the maths and modules - you are free to take exactly the same content within the BA Econ as you are in the BEconSc. The only benefit i see of the latter is that BSc's are perhaps regarded as slightly better. However, with the right module options on the BA this counts for nothing.
As far as i am aware Manchester is a 'top-tier' university (not the same league as G5 obviously) and the Econ department is very good and well respected. In addition the BA Econ from Manchester is a very respected degree. I'm hoping to go into a top city job so if anyone thinks this degree isn't going to cut it for that then post your thoughts while my choices are still open to me.
Cheers