You are right about the UK VAT rate, i.e. 17.5%. I agree that on new vehicles there can be a cost advantage with a personal import from 'the Continent'. Indeed, I did that with my (new) 'premium German brand' of car in 2001 and saved about GBP 5 000 on a UK price of about 40K. I had expected to save about double that but the RHD price went up and UK price went down a bit. It was a time when the fraction of direct imports rose to about 8%+ (my calculation) overall and was probably much greater for the more expensive cars, where the saving was the greatest. For example, a neighbour bought a Porsche through an agency doing direct imports saving about GBP 10K. Not to be sneezed at...
Car dealers in the UK were feeling the pinch, no question.
FYI I bought my car in Germany, having checked with dealers in NL, France and Belgium. I could probably have saved more money by going to Denmark which famously had/has low pre-tax prices but it would have been too much hassle for me.
In your case (used car, higher VAT in home country), I would seriously look at buying in the UK. Saves you the cost/hassle of headlamps etc. BTW, the side of the steering wheel is not an issue, for me at least. I have owned and driven RHD for a long time on 'the Continent' and LHD in the UK, and regularly drive across from the UK now.
Under such circumstances, what is your incentive for buying in NL? Just so that you an carry your stuff across?
DAS
For direct contact replace nospam with schmetterling