Tuning Titan XS spring and guide questions (for HW97k)

I want to replace my mainspring with one from Titan XS. Unfortunately, I do not have access to a lathe to make a custom spring guide and top hat.



I found T.W. Chambers in the UK (www.gunspares.co.uk). They sell the springs, and also have what they call an "Ultra" spring guide and top hat.



Anyone have any experience with these spring guide parts, and/or this company? Or have other suggestions for a spring source, and spring guide source? Thanks.