Filler / Caulk for Oak skirting

[ln1234]

I would like some advice on the best way to fill gaps in the top of skirting we'll be fitting soon. The skirting will be Oak, and we will be staining/varnishing it to match a dark wood laminate we'll be installing.

We were thinking of using the following (from recommendations on other posts on here) - are there better alternatives out there?

http://www.cuprinol.co.uk/products/all_purpose_wood_filler_overview.jsp

Do I choose a wood filler colour that matches the darker stain, or the actual colour of the oak prior to staining?

Thanks