Fixed appliances over 2kw should be on own circuit mate
As ever, things are rarely that simple.
As the competant person, it is up to you to assess several things:
# the condition of the existing circuit
# the existing likely loading of the circuit
# and the magnitude and consequent effect of any increased load on the circuit.
As you've given us scant information about any of these items, we are in no position to help. There is advice in the appendices at the back of BS7671 to help you.
You mention the oven is 3500W. Are you sure? Many single ovens have a grille and oven element which may add up to this, but cannot actually be used at the same time. So you need to assess the actual max load of the appliance.
What I&T have you done thus far? Is the RFC in good order and what size OCPD will it have?
Is this a small kitchen, and so lightly loaded, or a massive place that looks like a Currys display?
Reconnecting the new oven to the RFC in the manner you propose (don't forget an isolator) is not out of the question on a 32A RFC, but more info is required to ensure the circuit is adequate for the task.