I'm no expert, but I think these need ericaceous compost rather than just multi.

Multi purpose compost usually has added lime and the azaleas don't like it.

If your soil is acid you could just shove them in the ground without benefit of added compost.

Many thanks for all advice

You can get an ericacious feed to put in the ground when you plant, but it would be best to add some peat, or leaf mould, or even lots of pine needles to the soil before planting, as this would add the acid content to the soil that they need, as Bulbaholic says. Annie