Great stuff! Have fun with them!
You said they'd been fluked - what about worms? If you are bringing them on to clean grass, I'd be quarantining OFF the grass and doing a faecal egg test, then taking your vet's advice on treatment. If you've got clean grass, you don't want to bring worms on - you may never have to worm. Fluke you can't do much about as deer, rabbits etc carry it too.
Avoid combined flukicide / wormers like the plague.
I would do them with an external parasite treatment soon, but since they've been sheared, the risk of fly strike is less. I always did mine after shearing but let the fleece grow back a bit - maybe a couple of weeks. There is a variety of products - Clik, Clikzin, Crovect, Clik Extra - to name but 4. These have different dosage rates, pack size, price, length of efficacy and they don't all do the same thing.
For example, of the four above, only Crovect is suitable for preventing and TREATING fly strike and it prevents ticks and other parasites BUT it only lasts 8 weeks. The other three prevent fly strike only but all, I think, last longer. Clik Extra lasts 19 weeks, so should cover the whole fly season with one application.
With your small numbers, piggybacking on someone else is a good idea, if they are using the product you require. However, legally, only a vet can split a POM product like pour-ons and wormers / flukicides. Latrely, when we only had a few sheep, we bought wormer, if we needed it, and flukicide from our vet and just bought the quantity required. More expensive per dose, but far cheaper than buying a 1l pack then ditching most of it when it was past the use by date.
Vaccines likewise can only legally be shared by a vet, but it goes on, for the reasons you say.Just remember, most vaccines must be used within 8 hours of being breached - and ignore those who say "ah, just keep it in the fridge". Vaccines are pretty cheap - why risk it?
I used to get my butcher to price cuts individually, according to what he was charging in his "posh" shop. If you can get folk to pre-buy boxes, that helps your cash flow - and take a deposit (non-refundable) to stop folk messing you around.
Tags, unless your sheep lose some and need replacements, you won't need until your first lambs are born, so you're a whiley away yet. We used bubblegum tags from Allflex. Came in 10s. Found they pretty sticky.
Hope this helps and enjoy.