I’m in the market for a new roofrack and couple of bike carriers due to new car. As a tart i want the black rack and bike carriers – roofracks.co.uk show cheapest but line me up your best ideas for discounts. I’m a BC member so Halfords would get down to roughly same price.

Not sure about colour being important.
If you are set on the roof fix, then 1st decision is Original equipment or other for the cross bars. If there are no rails on the car then I would want to pay for the original genuine accessory roof bars, because they will be well matched to the vehicle body. The steel is pretty thin on most cars and quite easy to dent if the parts are not well matched. If there are roof rails then you can only damage a small replaceable bit so less risky.
Regarding the bike carrier the options are fork, frame or tyre grip style. All have different costs/benefits. Be careful with carbon bikes as frame and fork mount are not recommended by most manufacturers.carbon frame bike racks
Finally watch out for low bridges

I got some very good prices on mine with Tredz using some voucher codes i found online.
Worth a look.