Im usually in the housplant forum asking question after question but now ive found my way over here, so hi. :)

Ok so like everybody or most ive been reading Als links but im struggling to find ingredients for his mix.
I was wondering if anybody could offer me some simpler alternatives that would be readily available and improve on mine?, im in the uk but I guess main stream ingredients would be the same here as us (I hope)
Im going to be potting some new plants and redoing others so I want to get everything right finally lol

My biggest priorities are medium size Arecas and a large kentia (on its way), secondary a Ficus Benjamina and Canary Date Palms. Currently im using John Innes no2 with 1/4 perlite.
John Innes is
7 parts Loam
3 Parts Sphagnum peat moss
2 parts grit/sand
Added Fertilizer
Added lime/chalk

More im learning about potting mixes more I realise what I thought was right was wrong.
Could I add coir to the mix to add areation and extra perlite for drainage say John Innes,coir and perlite in equal parts.
Or maybe orchid mix or orchid cactus mix 50/50?
Are there light fibrous multi purpose composts better?