Argh Labels! (Carrots)

Y'know, every packet seems to be different!
So frustrating!

I've got a packet from last year that i didn't get around to planting due to being on crutches whilst pregnant with a terribly unsuitable garden.

I thought i'd plant some carrots in pots and dug out my Unwins Carrot Rainbow Mix, nowhere on it does it give even a rough idea of length! I have no idea what pot to use!
 It says sow direct but I've only got this month and June to sow and the little plot im getting ready won't be ready for a few weeks so I want to get shifty on.

Any ideas? Also, I saw something on the TV on BBC about growing in sharp sand...any need for this in containers or just compost? Or miracle grow vegetable? Or what?
Total newbie here so apologies if this has already been covered and i'm rehashing but i did search and only found a suggestion for Amsterdam Forcing and i'd rather use the seeds i have if i can. 

Thank In Advance!

Fab! Thanks! Our garden faces, South west, moreso west. So they should be fine!
I'll get them in asap Wonderful!
xxx

If you read the seed packets and be guided by the sowing times. You can sometimes give a bit of leeway but generally they are a good guide

Carrots like a light soil and I've found just compost works well for carrots. Sand in there is fine but not too much as you want lightness for those carrots to get nice and long     Don't sow too thickly!