That wall has been used for climbing purposes since I moved to Liverpool over a decade ago. I used to go down there and traverse backwards and forwards for literally hours. Wearing a walkman (to blot out the shouts of Scallies) and perfecting different eliminate ways of getting up, down and across the various walls and buttresses. It's how I got my legendary stamina.
There's nothing too hard on the walls but it is a nice spot to spend a bit of time bouldering if you can't get to Pex.
There is a better, harder, but smaller wall very close to Aigburth Vale too. It's vertical and made from solid blocks that offer "natural" holds and many small chipped edges between the blocks. This wall has a few decent up problems and a range of traverses for the initiated but probably needs gardening underneath to remove the long grass and brambles. To find it walk into Otterspool Park via the gate at the Aigburth Vale end of Jerico Lane and turn left immediately once you enter the park through the big gates. The wall is basically the large wall supporting Aigburth Road by the lights! The best problems are the fairly highball up problems just right of centre.
Having typed all that, I'm actually quite psyched to clean it up again. Mono, it's about 200 yards from your house!