I had to replace a tiny bit of skirting and have found that by painting it white gloss it definitely doesn’t match the existing skirting! 
This is odd because on first glance the existing skirting looks pretty white. But it must either have aged or it isn’t and never was ‘pure brilliant white’.
I’ve accepted that, annoyingly, I’ll have to paint all the woodwork. But pure brilliant white or a slightly creamier off white? (If you have the latter and like it could you tell me exactly what colour and brand you used?)
Basically, what colour are your skirtings?