Yeah... I'd be worried about weeds too especially if there are any perennials or an extensive seed bank. You really don't want to be dismantling your rockery to get at resprouting ground elder or dandelions (Ian's pet one notwithstanding!). What are the weeds?
I suppose the question also is whether Colin is after an ornamental bank or something that is a bit more of a haven for rare alpines. I mean you could get pretty good weed suppression and a fabulous display with things like Geranium cinereum, dwarf pinks, rockroses, Sempervivum, Erodiums, saxifrages etc. Bulbs too if there is enough soil. Phlox douglasii? There was a thread about a N American garden with a colossal rock in it with nice cultivars of this species on it. Dwarf willows are highly recommended if it's not too dry... a photo of the site might help. Some of the easier auriculas are great and can look really exotic.
If you are into something a bit more challenging, have a think about alpine habitats: crevices, rock ledges, scree, etc. Use the rock available to create sunny and shady, wetter and drier niches that coould provide habitats for more difficult plants: Ramondas; Drabas; dwarf Campanulas, Edraianthus, gentians. It's well worth getting hold of some seed from a seed exchange of a reputable rock gardening club such as might occur in Caledonian areas. That will give millions of plants to experiment with.
The other thing... have a think about access to your bank for maintenance. This could be actual steps, or strategically placed rocks depending on your agility.
I believe Pottertons Nursery are opening up again shortly, maybe he should speak to them for ideas once he is ready.
