Under Floor Draughts-Insulating

Hi Everyone
Hope I have posted in the right forum
We moved into a 1920's house a year ago and over the winter have been aware of how much draught comes up into the house from a fairly large crawl space under the house

I'd like to insulate down there-I have searched and seen suggestions about mineral wool held up by chicken wire onto the underside of the beams (although, and I know this is daft am worried that that would make it an attractive home for vermin??)

I have also read about polystyrene blocks that can be cut and wedged into the gaps between the wood rafters and saw some products on a popular DIY store. One was called Jablite Flooring Insulation Polyboard and the other Kingspan Thermaboard Urethane Insulation

So, please could I ask for your advice-what would you recommend??
To be honest the boards seem much easier to fit for a klutz like me but am willing to take advice
If the boards are the suggestion what thickness should I go for??

Many many thanks

sorry, I should have said I realise the importance of sealing skirting boards etc-I am wanting to know about improving insulation and try and cut down on heating bills through loss from under the floor
Thanks