[Watford] Broadband Access problem

[Cliff Deamer]

I need a little help!
I use a network of 3 PC's which on a normal day would be sharing
broadband access via a Netgear 834GT wireless router. My contract with
BT is for a 2MB/s service.
One PC is wired the other two are wireless.
Normally everything is switched off overnight and is fired up typically
around 0700 each day.
Over the past few months the delay between switch on and getting
connected has been increasing, starting as a few seconds it is currently
more than 30 minutes.
When it does connect,after a short time it may then disconnect, taking
perhaps an hour or more before it reconnects.
I have had a BT "engineer" check the line, he tells me it is good for
3.5 MB/s.
I have spent ages on the 'phone to Netgear trying their suggestions and
they assure me that the router is good. I upgraded the router firmware
to the latest version.
I have tried operating with just the one PC plugged into the router and
get the same result. I have also tried a single wireless connection from
a different PC with the same result
The problem is exactly the same if I use Windows XP or my usual o/s,
Ubuntu 7.04 (Fiesty)
My last resort is to go and buy another wireless router but before I
spend my hard earned, does anyone have any other suggestions?
All contributions gratefully received!
Cliff