No. do not use it on the plane. It could well be more hassle than it is worth.
You will have to carry it through the airport building as well as down the aisle and you'll likely have enough to carry as it is. Those things can be heavy to carry. If you do bring it with you I would pack it well and check it as hold baggage.
VA seats are very narrow and most car seats do not fit the seat dimensions It cannot overlap the seat either.
From VAs website:-
"If you’re travelling in Economy, you can bring your own car seat onboard all our international and domestic flights as long as you’ve booked a seat for it.
If you would like to use your own car seat, it must:
Be designed to be secured by means of a normal aircraft single lap strap
Have a separate 5-point restraining harness
Not exceed the dimensions of the aircraft seat, and should fit into an area of 43cm x 43cm (17.ins x 17ins)
Must be secured to its host seat at all times of the flight
If for any reason your car seat cannot be fully secured, it may have to be placed in the hold. In these circumstances, your infant will have to be secured to your lap whenever the seat belt sign comes on
The car seat must also display one of the following labels:
EU approved labelling
Approved for use in motor vehicles according to the UN standard ECE R 44, -03” or later
OR
‘Qualification Procedure for Child Restraint Systems for Use in Aircraft’
(TÜV Doc.: TÜV/958-01/2001)
And there's more as well:-
"Please note:
- You may be asked to show the approval labelling to our ground staff and cabin crew, so please make sure you know where to find it.
- You’ll need to show our cabin crew that you’ve fitted the seat securely and in accordance with the manufacturer’s instructions.
- The seat must fit securely using a normal aircraft seatbelt, as unlike cars, we don’t have ISOFIX systems or seatbelts that are worn over the shoulder.
Premium Economy and Upper Class
If you have a car seat, you may be aware that you can’t use them where airbags are fitted. As all of our Upper Class suites and the Premium Economy seats on many of our aircraft have airbags you will be unable to use your own car seats".