Planting blueberry plants in clay soil

Hi all, I've bought some blueberry plants for the allotment which has heavy clay soil, I've also bought a couple of bags of ericaceous compost to plant them in, do you think it will be ok if I dig a bigger hole than needed and fill it with the ericaceous compost? Is there anything else I should be doing to give them a good start? Thanks.

If you can check the soil PH to see what it is, clay can have a very high Ph

i've cut old water butts or similar up and used the bottom third, drilled holes for drainage and suck into the soil.

i'm hoping this will save the acidity leaching out, but also be big enough to give a good size bush.

it was the first year for them last year and they seem to do really well, i have topped them up with more acid compost to try and maintain the acidity.