May I recommend Earls Performance Brake Lines Telephone 01327 858221
https://www.earls.co.uk sales@earls.co.uk
I sent off my order to EARLS by 1st class post on Wednesday & had a phone call from Alan Poole on Thursday morning with a quote for £28:82 including postage to make up a 800mm one piece front brake line as per CB750K8 USA import with stainless steel fittings at both ends, Got it back this morning including 1st class postage back a quick fast service and the part looks perfect to
If you get them to send it back via Royal Mail P&P works out at £3.25 as they will want to send it coruier which will cost you more
Hope this helps you to finish your project