In reply to bpmclimb:
£135 for 10.5mm Beal Contract https://access-techniques.com/product/beal-contract-10-5mm/
They also do 11mm English Braids which is ~£1.67 per m, I've been quite happy with the performance of my 70m static rope in terms of its durability.
I remember them being notably cheaper than anywhere selling thinner static ropes when I bought mine several years ago, however having dragged a 100m 10.5mm static around Lundy for a week I can well understand why you would want something thinner!
Possibly also try some of the caving places like Starless River, or Inglesport (from what I remember there are two types of semi-static defined in the standard with one being strongly preferred for the abseiling into sea cliffs and possibly needing to ascend, but I can't remember which is which and am about to go to bed, I'm sure that one of the cavers on the forum will be able to give you the correct information around this).