Bromptons are cheaper to buy in Britain than the US ( e.g. S6-LX )
The US Importer is make a good markup !

US - CA : $2082 plus 9.25% = $2274 = £1380
UK: £1085 inc 15% VAT = $1788

The reverse markup also seems to hold for Tikit pricing
Again the Importer is taking a good cut.

UK: from £999 inc 15% = $1646
US: from $999 plus 9.25% = $1091 = £662


Here's a link to the UK import rates for complete bikes : 14% duty is normal, with the exception of additional 'anti-dumping' rates of 48.5% applied to Chinese sourced bikes - though you can buy up to 300 chinese frames per month at 1.2% duty.