Custom sensor to go in your config.yaml, looks at PV power and takes off 4100, this allows for 3600 export and 500 to go to cover house baseload, the battery will charge at 500w as well as I only modify the charge rate register not active power:

sensor:
  - platform: template
    sensors:
      charge_rate:
        friendly_name: "Dynamic Charge Rate"
        unit_of_measurement: "W"
        value_template: >
          {% set original_value = states('sensor.givtcp_XXXXXXXX_pv_power')|float %}
          {% set adjusted_value = original_value - 4100 %}
          {{ adjusted_value if adjusted_value > 0 else 0 }}

Will need to create a custom helper called "prioritise export" and I keep it as a toggle switch on my dashboard so I can just tick it on.

Automation, runs every 60s and stops at 1544, times up to you:

alias: Prioritise Export
description: ""
trigger:
  - platform: time_pattern
    seconds: /60
condition:
  - condition: time
    after: "06:00:00"
    before: "15:44:00"
  - condition: state
    entity_id: input_boolean.prioritise_export
    state: "on"
action:
  - service: number.set_value
    data:
      value: "{{states('sensor.charge_rate')|float}}"
    target:
      entity_id: number.givtcp_XXXXXXXX_battery_charge_rate
mode: single

Automation to set the charge rate back at 1545:

alias: Prioritise Export - Reset Charge Rate @ 1545
description: ""
trigger:
  - platform: time
    at: "15:45:00"
condition: []
action:
  - device_id: 5f75f57ebceacf500a639469e4eef245
    domain: number
    entity_id: 33e17bf2448db1cdb887317c4a517366
    type: set_value
    value: 2900
mode: single