A couple of comments on Investors Europe and Saxo :
Investors Europe seem to be willing to discuss rates, and use several platforms - the cheaper is TWS, where they charge an extra fee on top of IB (I guess also one has 2 counterparty risk, with IB and IE), they have also have other platforms with more markets than IB offers, but rates I got after quite a bit of haggling were not attractive, quite a bit higher than their TWS offer. Also who has actually experience with them ? There is hardly any comment abt their services on the net. Once one of their rep showed up on this forum and disappeared as fast as he came before answering any question.
As of Saxo, I'm not sure what they offer to institutions, but on their european websites , they offer a platinum account with a 500keuros minimum where one might get more competitive rates without the need for larger volume. I went to see them in HK and Saxo HK doesn't have the platinum account, same conditions for customers opening a account with 10k or 1mil. It gets less expensive with a significant volume. Horrendous commissions and margin rates.