Depends on whether you intend to put acid-loving plants or just run-of-the-mill ones, i.e. seasonal bedding plants. If you are going to put permanent plants then J.I. No. 2, soil- based compost with a little multi-compost would hold moisture and nutrients best.

Yes, Westland with John Innes no. 2 is great. I believe compost is all ph neutral unless itis specifically ericaceous (acidic) which you will need for heathers and dwarf azaleas, rhododendrons etc. Bit otherwise you will be fine. Enjoy planting, they sound lovely.