how deep do you have to go for a footing for a brickwall with block&beam for a patio???? any help

Not sure why you would need to go to the cost of a block n beam for a patio???? But a simple 300mm x 300mm concrete trench fill would do

i would go minimum 500mm at least get solid ground,225mm concrete

There is no definitive answer to this question without knowing the ground conditions. For example is you have bedrock just below the surface then you only need to use concrete to give yourself a level platform to build off, on the other hand if your ground is like a peat marsh then you’re not going to find suitable ground to build on and you’ll need pilling done to achieve a foundation. Do you know what your house foundations are? I’m assuming if you’re building a block beam patio it’s going to be elevated. It may be a good idea to get a local structural engineer involved to design everything for you.