Thank you. The contract you have is for the GBB Ltd company only so the employer can only apply these terms against you if they are relevant to that company. Looking at the terms in there, the only relevant one is Confidentiality, on page 2.
This clause says that after your employment with that company terminates, you cannot disclose to anyone information about the company and its business dealings or customers.
This does not stop you from setting up in competition with them or even working with their old clients, especially if they approach you.
What will make this clause difficult to enforce is that the period for which this restriction applies is unlimited. They should have set a specific period for its application if they wanted to make it fair and enforceable. An indefinite restriction will make it very hard to enforce.
In terms of your relationship with GEB Ltd, there is no contract in place and as such they cannot really prevent you from doing anything similar if it relates to that company. They cannot apply the same terms as GBB Ltd to GEB Ltd and if they wanted to do that they should have had a formal written contract with you, which they never had.
I trust this has answered your query. Please take a second to leave a positive rating by selecting 3, 4 or 5 stars above - this is an important part of our process and recognises the time I have spent assisting you. If you still need me to clarify anything else, please reply on here and I will assist as best as I can. Thank you