Hi Bluebird, I believe Kitshack have gone out of business, however I found one of their kits on Ebay from a seller called Collectorslottoo in Norfolk.
Their advert said they had sold 10 and mine was the last one and their advert was as follows
Back by popular demand. RAF RTTL kit produced with pre-printed balsa and quality Birch Plywood parts ready for cutting out and assembly. Includes balsa and dowel for final finishing to complete davits, mast, etc, Kit includes full size plans and full instructions. Kit excludes paint and finishing materials but everything else is in the box, for cutting out with basic craft knife and fine saw, glue, and sanding block. The photo in the listing is one of our completed models, made by a previous purchaser. Suitable for R/C to use a 400 or similar motor. Motor, prop shaft, prop, rudder etc. is not included in the kit.
I researched Kitshack a little and it seems they were a small company that had lots of plans and made kits up to order but Company House says they are now dissolved so maybe this is old stock or somebody else is doing the same thing??