For what purpose?

To do...

Whatever you want it for, buy good quality soil from a reputable source.

If for veggies then you will need to dig in well rotted manure/compost now, ready for planting next year.

You must make sure the manure is well rotted, for at least one year, 2yrs is better.

'Which' do compost trials, if you enter this into google then it will give you some webpages that contain the information on what is the best compost as per their trials. B&Q Multipurpose was top of their rating in the '10 trials, but whatever compost i buy it often seems to change in its make up, as if they change the recipe from time to time. Often different batches of compost differ too.
I think most compost you can buy at the garden centre should do the job fine, personally i have not noticed a specific brand excel.