Credit cards and mortgage application-ready credit file

E&G

Hi

I am looking to get my credit file as good as it can be for a mortgage application, probably in April/May of this year. I currently have three credit cards:

• Barclaycard - Used to balance transfer from previous M&S card. 0% until next month with no additional spending. £1500 outstanding with 4k-ish limit.
• M&S - transferred balance to Barclaycard last year with no further spending. £6000 or thereabouts limit.
• Aqua - used as first 0% card until offer expired then cleared c.3 years ago and never used since. Limit reduces every six months or so and is maybe £1000 now.

Any advice on whether I should keep the M&S and Aqua cards open or not (showing I don't use available balance/I have available balance to use), and whether I should hang off balance transferring my Barclaycard until after any mortgage application would be much appreciated.