Don't get me wrong, Manchester finance is definitely solid but for some reason I'd assumed that you came from a better uni/course given how impressive your offers are, I've seen people from top top unis do much worse in master's applications so you must be a solid candidate so you definitely be happy with these offers.
I think the general consensus is that LSE's MSc Econometrics & Mathematical Economics is the best European economics master's, it's got by far the best track record of placing students into top US PhDs than any other European course. But Oxford I would say is number 2 and better than LSE's straight MSc Economics.
I'm of the opinion that if you're wanting to work in finance then doing two years of theoretical economics probably isn't the best use of your time and £36k + 2yrs of living costs + the opportunity cost of the extra year relative to one year courses. The MPhil program there is definitely rigorous, I'm just not quite sure how stuff like real analysis, advanced mechanism design and even lots of the advanced microeconometric methods will have very very little use in a finance career. The course would only offer you two optional financial economics modules too, the macro ones might be useful but grad level macro is stupidly theoretical with pretty unrealistic models which are only useful for specific central bank stuff, either that or they're variations of long run growth macro which again is useless in finance. The Ox course would be great PhD prep or even really good if you wanted to go into economic research teams at banks/consultancies, but not normal trading/IBD roles imo, it's not bad, it's just not that relevant.
Whereas the LSE and Imperial courses will have a decent degree of theoretical and applied finance and have brands that will be more than enough to get you into a bank/fund if you're a decent candidate. AFAIK, there aren't many companies that would hire Oxbridge but not LSE, a lot of the most elite firms in finance/consulting seem to hire from Oxbridge and LSE so I think you'd only ever experience that problem if you went to somewhere like UCL or Warwick, think you'd be fine with Imperial too, and this is just for the most elite small companies, banks hire from a wider range and hire from LSE far more than Oxbridge nowadays (again there are many reasons for this tho).
Ik some corp law firms are Oxbridge only but the most elite firms I've found still hire from LSE as well as Oxbridge so I don't think it would affect you prospects at all personally.
Ultimately, it's your decision so just go with whatever feels right for you in terms of modules, career path and cost.