im looking for a lightweigtht rear rack to fit my custom built cross bike, 700cc with disc brakes for a upcoming tour of pembrokeshire, also a set of bags to suit, help appreciated

cheers

Does the bike have rack fittings? Either way, there are a few options, but you're going to be limited if you want to use disk brakes (unless you've put the disk mount on the chainstay).

Bags - just pick a price point, then Altura, Ortlieb, Carradice, Edinburgh Bicycles. 

I have a Topeak rack designed to fit with disc brakes, but it's not lightweight though! 

And men have a habit of commenting on my "wide rack"  - don't think they're refering to my @rse

You might be able to mount a Tubus rack using their QR adaptor, depends on the clearance and the angle of your seat stays. I've been using Old Man Mountain Sherpa racks for the last few years (pic). If your tyres aren't too big the standard model should work with 700cc wheels. The normal Sherpa will work with hydraulic disks, but you'll need the extra clearance of the 'DISK' model if you're running mechanical disks (such as the BB7s I have).

I have tubas racks fitted with disk brakes, on one side I have fitted them to the disk brake fitting, on the other side I have used the extension part which as they come in a pair, means I have a spair.If I get a chance later this afternoon I will take photos of how it is set up and post them.