The best thing to do would be to keep the existing router in it's place.
Then buy a secondary cable router for around £25. Run a cable, say 25m of cabling (you can get this on ebay for around £2) from the existing router to where the signals currently poor. Place the 2nd router at the end of this cable. You just need to turn DHCP off on the 2nd router and it should work.
This way the broadband signal is unaffected in anyway and you have strong signal all over.
Moving the existing router just a few metres is likely to marginally increase the signal in currently bad areas meaning you'll still have low signal in some areas. Also moving it might introduce new areas where the signals bad.
Edited by ukhardy07 (Mon 07-Oct-13 01:26:25)