I think it's fine to ask for references from your previous employers but if they haven't worked with you under your company name it would be misleading to have them imply that they had.
Most of my references/testimonials just refer to me by name anyway - so by all means, collect them and use them to your advantage but don't worry about the branding thing. You'll soon enough have plenty of tesimonials from clients who can vouch for you by company name without hestitation.