I'm wouldn't be a fan of travelling to the UK for a car. The Irish log book doesen't take into account any previous owners from the UK, and its not easy to sell them on. Also, if you had a problem you can't exactly go back to the garage easily.
I've been burned in the past so any car car I buy has to be perfect. 1 private owner, with a full service history. I get a mechanic to check out the car fully and do the cartell checks.
Here's another example of where the cash is king philosophy is not holding true (for me anyway)..
I went to see an 06 X5. Dealer is looking for 50K for it and say it has been recently reduced. Best they will do for cash is €48k, and wont go any lower.
What's even more surprising about this is that they have had the car for sale for over a year.