Core drills

Miss P will look some up for you.

But in the mean time, these are good.

http://www.screwfix.com/p/erbauer-3... Accessories&gclid=CKXg59b4g8cCFRQatAodCLALww

 

Suprisingly these seem quite good, not usually a fan of Erbauer,especially their power tools.

A 5 piece Mexco set here:

http://www.sitebox.ltd.uk/mexco-11-...paidproducts&gclid=CIH1htD5hMcCFSrpwgod8EsOdQ

 

Covers every hole size you will usually need.

Might find looking through Quidco for the Mexco set, might save a few more pennys.

 

Never had a problem with them, use a lot Mexco stuff, like diamond blades.

http://www.mexco.co.uk/Products

 

In the MEXCO set they have a 117mm and a 127mm core. Is one for 4" and one for 5" holes? If so what are they only 10mm different? I have a 127mm and it is a pain in the rear to get a 5" duct hose through.

 

Duct hose is slightly larger diameter due to ribbing than 125mm rigid ducting.
It's about 132mm overall diameter if my memory is correct.