I suspect you'll have problems sourcing British Made parts. Labelled or packed in Britain, perhaps.
The capacitors you suggest will no doubt perform just fine, but they'll cost plenty compared with plain vanilla good quality film capacitors for very little if any performance advantage.
Arcol (Ashburton Resistance COmpany Limited) is British (at any rate British based) but Vishay(-Dale) is American based and again likely manufactured anywhere. Vishay make no bones about having started out in precision resistors but then expanded by takeovers into a broadline component source. Dale was just another company they acquired with a decent reputation so still included by name in the resistor brand.
Have a look at the likes of Vishay and TYCO (Takes Your Company Over)
and their history and you'll get the idea.
Plenty of globalisation to be found in electronic component manufacture and supply
