Darren, after a lot of web searching a phone calls i think i have got somewhere regarding part numbers for the Oil Filter. Ignore the earlier link i sent you for K&N filters. Thats the old cross reference and wont match yours.
Bryco 01327 - 876166 (
www.bryco.co.uk)
Genuine Kohler CH20 Oil Filter (Part number 1205001) £9.35 + VAT & carriage
In-Line Filters 01579 - 321351 (
www.inlinefilters.co.uk)
Non Genuine (part number FBW-B1410) £9.10 + VAT & carriage
Non Genuine (Part number FFR-PH5660) £2.72 + VAT & carriage
After a long discussion with the guy at in-line filters he told me that both of those filters will fit the Kohler Command CH20 engine.
Also, the UK's largest car parts supplier have oil filters in stock. Look at the 2 links below. The first (BOSCH) is the longer version, the second (HENGST) is the shorter version
http://www.eurocarparts.com/search/501560010/p/homehttp://www.eurocarparts.com/search/501745150/p/homeThe good thing about Euro Car Parts is that they have over 120 stores nationwide so you could go to one of their stores or opt for online with FREE delivery.
Also the FRAM part number is PH8172
Hope this helps.