There's a few things to consider about candidates from the UK.
The manager.
1. I'd imagine if you're not at the top table the money over there isn't fantastic anyway. Like is Baraclough earning much less at Sligo than he was at Scunthorpe??
2. The potential stature increase. Like say you're an English boss and you're tipping away doing a great job at Rotherham. Now obviously Rotherham is a much bigger club than Limerick but if you were to do the same good job at Limerick you could potentially find yourself in Europe. Pox a long ranger in Belgrade (:p) and you find your staure increased massively by comparison. Would Michael O'Neill have got the Northern Ireland job off the back of guiding Brechin to theupper end of the Scottish First Division??
The club.
1. Players - Limerick probably need two centre halfs, a left back, two wingers and a striker. I wouldn't say no to a couple of Gary Twigg types.*
2. Profile - As nigel says in theory a big name could attract a couple of hundred extra fans which in theory could lead to a grand a week extra for the budget/the bosses arse pocket. Hard to quantify and maybe a dangerous road to be going down.
There's negatives as well of course. He probably isn't familiar with the culture/standard and the club isn't familiar with his personal circumstances for example.
*if we got a couple we could play them as two stopper centre halfs.