Time to resurrect a long dormant thread.
Despite my best efforts 11 months ago, a new router was not forthcoming. SWMBO decided that it was not really required and after all the playing around with Vistumbler, as described earlier in the thread, the connection was far more reliable although still on the slow side.
However, last night the old router finally gave up the ghost. As SWMBO has upgraded laptops recently an 802.11n router was the obvious replacement. So, to cut a long story short I am now connected via a D-Link DIR-635 which I picked up for 399 Swedish Kronor, approximately 37 Sterling.
After I've had a chance to run Vistumbler I'll post some connection speeds. Will be interesting to see if there is any appreciable improvement in speed.