I wonder if anyone can tell me what compost to use for the beautiful
Hydrangea I bought from Lidl's this morning.

Anything well drained should do. Much as I hate Hydrangeas myself, they do
seem pretty robust.

Oh, what colour flowers do you want?

Hydrangeas are like litmus paper in reverse - Acid soil = blue flowers,
alkali soil = pink flowers, neutral soil = white/cream flowers. Although
our solitary Hydrangea is pink despite neautral soil.

Al.