Are airbricks too big for my walls?

Could be just lack of insulation, or yeah coukd be there's to many air vents for the space there is, thats why there's so much draft

Your neighbour is risking damp/rot by blocking airvents in the winter, so don't go down that route. You need to provide a barrier from the cold air beneath the floor. Hardboard over the floor boards before adding the laminate/underlay/carpet.

Ultimately, ripping up the floorboards and
insulating between the joists will be the best long term solution, and despite the inconvenience/cost, will save you money on bills and make the room much warmer.

Hi you could reduce them to the size of one brick reduce the cold air flow
And maybe block the solid wall one up aslong as there’s no gas appliances in either room

Are these vents venting directly into the rooms or just into the underfloor area?
If they are only venting the underfloor area then I would suggest not reducing the underfloor ventilation. Instead you might consider insulating and reducing draughts from under the timber floors.
There are plenty of threads on this topic.

As the kitchen is an extension, the builder may have provided a channel under the concrete floor for the continuation of the under floor ventilation for the rest of the house. Have a look at this link for a better understanding, and scroll down to the photos:

if you don't want mould keep them open, this is to keep air flow underneath your floor.

The size of the airbricks in your rooms could indeed be a contributing factor to the coldness you’re experiencing in the winter. Larger airbricks allow more cold air to enter the room, which can make it harder to maintain a comfortable temperature, especially in poorly insulated or draughty areas. In your case, having 9x9 inch airbricks on the side walls and 6x9 inch airbricks on the front walls may be allowing too much cold air to enter the rooms, particularly if they are not adequately sealed or insulated.
One solution could be to replace the existing airbricks with smaller ones or install airbrick covers with adjustable vents to control the airflow, you should also ensure that the rooms are properly insulated and draught-proofed to minimize heat loss and improve thermal comfort. This could involve adding insulation to the walls, ceiling, and floors, as well as sealing any gaps or cracks around doors, windows, and other openings.