Blueberries by nature need slightly acidic soil anyway, however you won't be adding enough compost to really make a difference. Just add a moderate about. Changing the soil Ph factor isn't easy.

Our council compost tends to be neutral and they take 'pride' in saying so when they dish it out for free.

it will be suitable for your blueberries yes. I assume you are growing them in pots then. If you pop them in the ground add some around/in the planting mix too. if you are worried that they are not in the right pH then water them with a suitable feed for them.

Ah... that's good to have this verified as I didn't really believe my friend. He used it for the first time on his veggies instead of manure and he said he had them growing really well. (Not dug in, just heavy mulch before planting out the seedlings).

My other blueberries have been mulched with pine needles that I gathered from a forest (under the top layer as its more decomposed). Do you think if I dug deeper, I could use this soil instead of compost (council or proprietary), this way it'll have natural bacteria in there and soil based.

When you dig around your blueberries, be careful not to hurt the roots as they are shallow rooted, however just applying it to the surface, it will work its way down to the roots anyway. The pine needles are really good for acid loving plants. I throw a couple handfuls around each plant every fall. A pine log under each bush would be good for years.

Why a pine log? I'm afraid mine are grown in pots and so I don't have space for them!

I don't think my small bushes will yield to much this year as they're only about 12" tall. Each variety all vary in the number of branches - Above pic of Ozarkblue has the most branching, followed by Bluecrop and Goldtraube being a few. I found Ozarkblue (my first 7 years ago really starting producing after 3 years in a big pot, but with last summer's heatwave, it nearly died and have just the main stem left and a few little branches.)

Pine log takes years to break down in lieu of pine needles. It also adds a decorative element. But mine are in a planting bed, not pots.

Are you certain that the council made compost is intended for use in pots? Only it often isn't, its used more as a soil conditioner in open ground...

And I hate to be the one to say this, but pine needles are only acidic ( and even then only slightly acidic) in the green state - once they're brown they're no longer acid, becoming more neutral in ph. Should you collect some again, get the green ones.. You might be interested in reading the link below on this subject first though

https://www.gardenmyths.com/pine-needles-acidify-soil/

As for digging deeper into the forest floor and putting that in your pots, no, don't. First, it may harm tree roots in the forest and second, it won't necessarily be acidic anyway, and third, you don't know what pathogens might be present which, whilst free in open ground cause no problems, but may cause problems in a contained environment such as a pot.

Using ericaceous potting soil is a good way to ensure the soil in the pots is acidic... and sequestrene iron tonic periodically helps too. As for bacteria or biodiversity in the soil in your pots, once a plant occupies the soil, various life forms will arrive anyway.

Bamboo:

I'm not sure what the council's guidance on the compost uses are for. It's my friend's first time last summer when he bought some for his veggies. He's said he'll be using it again as it's a lot better than manure where you have to break it up and often it has weed seeds in it, whereas this compost doesn't.

Thanks for warning me about digging up the forest floor. I'll stick to gathering the pine needles for mulching only. Are there other alternatives I could use for feeding ericaceous plants without buying anything. Is comfrey tea okay on them?

If you mean for your blueberries, its fine to use, but you will need to add a source of phosphorus, as they're fruiting plants. Bonemeal will provide that in theory, but it takes years to break down...

Pine bark is a very good soil conditioner for blueberries. Not only does it retain its acidity, but it also releases other important nutrients such as nitrogen, potassium, phosphorous, iron, magnesium and other minerals to the soil. The only problem I see is that you have your plants in pots and everything washes out the bottom.

https://homeguides.sfgate.com/pine-bark-soil-conditioner-101383.html

How could I get pine bark? Are there varieties that are accessible to the public (arboretums etc.) where there is peeling bark that I could collect?

The "greenwaste" you mentioned at the beginning should have it all ground up. Isn't that the discarded Christmas trees all ground up into mulch? That's what we have here. All the discarded Christmas trees all ground up into mulch is free for the taking & used in all the public parks. You should also find a good supply laying around in the pine forest.