If you've got over £7k to drop on some alloys then go for some customised HRE's, there are plenty of other ultralight forged wheels available for a bit less than the Carlsson options - I had a quote for some 19" Nutek forged wheels (something like 10kg per rim) from America, including import duty and shipping they worked out at £3k rims only, then get some tyres over here which would be circa £1k. So there are a few options to consider