bill001g is correct, you are talking about load balancing / pollicy based routing etc, line bonding is an ISP thing.
You should be able to ring up BT and ask them for a quote for a guaranteed bandwidth business line without involving an external consultant.
I assume you are a business not a home user?
Can you comment on what you are currently paying/can afford?
you seem concerned with upload? this suggests you are hosting something? adsl products typically have poor upload speeds compared to download.
Can I ask what services you are using your connection for and roughly how much data you are using for them, this may help us comment better on the viability of satellite etc, or perhaps external hosting, or more efficient use of some services.