Apple have literally just changed the $ for £ on the UK pricing lol.
but UK prices include 20% VAT - US prices don't include sales tax.
At times, last year, the £ was down to around $1.2, at which point $1=£1 was about right. The current "headline" rate is about $1.33 so $1000 should be a bit over £900.
However, the headline exchange rate is a pretty poor measure of what it might cost Apple to change their £s into $s, I have no idea if any import duties are involved, but there certainly are extra costs in terms of meeting EU/UK regulations (especially for phones), funding the longer warranty periods required by EU/UK, localisation etc. so maybe 10% mark-up isn't unreasonable.
If you want to cheer yourself up, ask the Americans how much they're paying for voice and data. Swings and roundabouts.
However, whether or not the iPhone X is worth $1000 is another question. I think my days of buying Android phones are certainly coming to a middle...