Halfords are selling a brand of Headlamp Bulb called “Simply”.
Are they an exact match for standard Headlamp Bulbs, hence you could just swap one, or are they different (brighter, different colour temperature etc.), so needing to be swapped as a pair?
I’m not seeing a “Simply” brand on Halfords’ website - just “Halfords” brand, plus Lucas, Osram and Ring.
If you put your car reg in at the top it should tell you what’s suitable for your car.
I think it’s usual to replace both bulbs at the same time as they tend to degrade at the same rate.
They’re available on Amazon.
https://www.amazon.co.uk/Simply-S499-H7-Headlight-Bulb/dp/B00NITNTGW?ref_=ast_sto_dp
OK so not sold by Halfords then. 
If I were you, I’d contact the Simply Store as they’re far more likely to have a definitive answer to your question. All we can do is guess…
Sorry, I put Halfords, when I meant to put Aldi. 
No one can say if they’re an exact match other than that they will fit in the same hole and have the same electrical connection. Bearing in mind that output changes as bulbs age, it’s unlikely that you’ll get an exact match but probably not enough of a difference to matter. If it might bother you then, since they’re almost certainly cheap, why not just change both at the same time.
You’ll want to fit a pair of them due to the 6000K colour temp.
In comparison, the Philips extreme vision H7s I use are 3300K and they are whiter than Casper The Friendly Ghost when he won the Daz doorstep challenge.
No mention of country of origin in the ad.
Cheap Chinese imports?
Given they cost less that any offering from Halfords, they are either stolen or made in China.
Well, other than Halfords being just about the most expensive place to buy anything for your car and most of their stock will also be made in China, you’re spot on.
That’s changed then as they used to be the cheapest for bulbs, spark plugs etc. because they got manufacturers to make lower quality and reduced cost products for them so they could undercut everyone else.
I remember my late father (an automotive electrician) bending his Champion rep ears about how he could buy the same spark plug from Halfords as a normal retail customer cheaper than he could buy it at trade price direct from Champion.
The rep’s answer was “You only buy a hundred spark plugs a year, Halfords buy hundreds of thousands and the ones they buy are made down to a lower price by using lower quality materials.”
Thank your lucky stars they are not HIDs, at £75 each!
That claim alone puts them into the “dubious” category. You can’t achieve 6000K with an incandescent lamp.
I’ve fitted them.
I installed them one at a time, and compared the “whiteness” of the light, and to be honest, I can’t see a lot of difference.
Anyway, I’ll have a drive when it gets really dark, and see if they appear any better than the regular bulbs.
True, a Xenon gets to that temperature. Halogens only around 3000k
I took the car out for a drive last night, and there’s maybe a slight difference in the “whiteness” of the lights, but it’s not alot.
You can, you just need to stick a suitable filter in front of it.
Indeed. My long career in stage, TV & event lighting clearly taught me nothing…. 
How so? You can filter out not filter in, if the temperature is not there to begin with?