Primroses are on single stems and polyanthus have several heads on one stem, not easy to see on a seed packet.

The plants you are talking about are all nursery cultivars from our native primose and cowslip. There is no clear definition between the two but it is usual to call the low cushion plants with single yellow/red/blue flowers primrose (as in our native primrose) and the ones with a cluster of flowers on a stem, polyanthus. Both names are interchangable.

Polyanthus can be split into its roots. 'Poly' meaning many, referring to the multi-headed type, i.e. several flowers on one stem, and 'anthus' from 'anthos', a flower. So, usually, that's how we define them. However, as they ALL belong to the same genus, primula, and have the same origins, quite often, as Bulba says, the names end up being interchangeable.

I feel like being interchangeable Worthy. Just opened the £3.69 packet of Primula seed, shocked at the mingy pinch in the corner of the sealed packet. Job to see whether there were 6 or 7 seeds. This is T&M.
I opened the packet of Mr Fothergills £2.15 Violas same thing - perhaps a few more but not many. Carefully
sowed both lots on the surface as directed, placed in poly bag to keep moist.
Its no wonder there are unsold huge displays of beautiful photographs on seed packets in GCs - nobody buys them. GCs going out of business every September.
I will in future wait for Mothering Sunday, buy Primulas/Primroses from GCs who seem to have the knack of getting value for their investment from the seed merchants. Do they deal direct with Kings for their
flower seeds ? What do the rest of us do ?
Has anyone else had this experience ? I was wearing my reading glasses, I could see them properly.
Cheating, cheating, cheating.

My supplier of bedding tells me, and I believe him, that primrose seed costs him pence per seed, and native primrose, 20 pence per seed! I run a small garden centre and I don't do much other than plants. It is a real struggle, and I barely make a living. I've given up supplying seed, preferring instead to stock (and hopefully sell) strips of veg and wildflowers as small plants. My dad told me, 45 years ago, that I'd never make money selling plants. It took me 'til now to realise he was right!

You are up against the Dutch growers Worthy. GCs arent allowed to order what they want. They have to accept what is on the container lorries.
Best to concentrate on plants they cant grow in Holland.
Then the real plant hunters will seek out your garden
centre.
One idea is small plants for small gardens. Modern housing Estates only give people a small piece of land.

I think that your supplier of bedding was pulling your leg, Worthy, if he claims he pays 20p each for primula vulgaris seed. A quick web search took me to Sarah Raven's site and she sells them at £1.95 for 500 seeds.
http://www.sarahraven.com/shop/wild-primrose-primula-vulgaris.html

Or ask me in early summer and you can have free ones...