defender td5 idler pulley bearings

Hi, been told my idler pulley bearings are shot, wondered werther to change just bearings or new assembly, just theres a big price difference between oe etc, apart from bearing quality cant understand why there so expensive, timken bearings are around 5quid! Plus does anyone know if the bearings in the two idlers are the same, pulled 1 number off google a 6303? Any suggestions?

I fitted new bearings in mine and it has been fine for the last 28,000 miles.

Cheers mate, it all went pete tong the day after posting, one of the bearing decided to explode and snap new belt aswell, so ye i got timken 6303 sealed hi temp grease, 16quid would of taken 10mins to knock out and fit but when i saw the crappy spacers/washers in one of the idlers then realised there isnt one in the other i machined some alloy ones up before refitting, thought id post that lot as i couldnt seem to find definitive answers