Well, I've looked at it again.
Own carPresuming we have one available
Going by car might be fun, but will take probably 2 days, and a large part of way would be on the wrong side of the road. It's somewhere between 1200 and 1300 kilometers to get there, which means we would need about 1300/11*2=236 liters of fuel. Now I'm unsure what the fuel costs are in the UK or whatever, but estimating from dutch prices we'd pay about 236*1,65=390 Euros in fuel alone.
Since we would need to either take the ferry or the eurostar, costs would rise even more,
but haven't been able to find eurostar prices.
Ferry would save us some Km's, but costs with 4 people are a whopping 300 Euros as well making it a say 650 euro travel or 162,50 Euros each. With less than 4 people it's even worse.
Flight+car rental
Better idea could be flying to Liverpool (cheapest UK airport from Amsterdam) and rent a car there.That would cost 237 Euros for the flight and another 150 for the car (387 Euros) + (~400 km/11*2*1,65)= 507 Euros or 126,75.
(In)direct flight + pickup
Alternatively we could fly directly to Glasgow from Amsterdam for about 205 each or fly indirectly to Glasgow for about 127,50 Euros each. As an adition we could of course rent a car here as well.