The cabin filter is called for replacing on the second service by MG ( ask them to leave the old one in the car - yeah ?).
The brake fluid replacement is an odd one TBH.
Different manufacturers adopt differing procedures.
VAG cars call for first replacement at 3 years, then every two years after that.
I know some dealers like to replace it, but on my car it did not get done at the time of the two year service.
The fluid should be checked for the presence of moisture content, if the reading is high, then yes replace it.
Replacing it provides revenue, but not checking it.
You don’t have to take it to a main agent, you can use a third party agent, but they have to use MG OEM parts if required.
Otherwise you could compromise your warranty.
Also if you use a MG main agent, you will get your free MG Assistance for another 12 months.
This is worth factoring into the cost of course.
Rear brake disc replacement has become the flavour of the month right now.