I picked up some bits from MES's Poole branch a couple of weeks ago - they are both owned by the same parent which is why things look so identical, but where they were once different companies, prices do seem to vary slightly!
When I picked up my bits, the guy in the Poole office was saying they are about to relaunch a new, combined website - maybe that hasn't quite yet happened.
They are a reputable company so I have no issues in buying from them, as as per Willk above, service can be variable. My last batch of stuff got sent to the Plymouth office instead of Poole, with no comms to me until I phoned up after a month to ask where they were. The first guy said he'd send to Poole and they would phone me when it arrived in a few days. 2 weeks later I phone again to ask where they are, and am told they won't ship things to the Poole office by someone else. He then phones the Poole office to discover my parts are awaiting my collection...
So if the price is right, do buy the kit, but monitor your order carefully!