thanks a lot for the advise and info kat, we'll look into all of those.
currently we don't have a microwave, although will be buying a new one this weekend, so i'll do tests before and after and possibly place the devices in different rooms, if i notice anything. i've also unplugged all other devices i could including our landline phone which shares the adsl filter/splitter.
i've been doing tests using speedtest.net at various times throughout the day and night, it seems consistant, other than on newyears eve when it dropped to 0.1mb but we assumed that was due to the exceptional amount of users sending messages etc to each other.