Poor Downstream speed

[scooby_snax]

Whilst I continue to battle with the BT Indian call centre i thought I would ask the experts here and more likely to get a sensible response.
BT Broadband subscriber with 2 Mb/s service
Yesterday evening I noticed download speeds had dropped. I ran a few tests and discovered downstream had dropped to 97Kb/s but Upstream was 368Kb/s.
Tried a few things like rebooting, switching off the router, clearing cookies etc etc to no avail.
Ran a test using the BT speed test and received this analysis
IP profile for your line is - 152 kbps
DSL connection rate: 448 kbps(UP-STREAM) 2400 kbps(DOWN-STREAM)
Actual IP throughput achieved during the test was - 116 kbps

As everything was working fine yesterday morning and wasnt in the evening when I returned from work and switched the router on I suspect it maybe either a line problem (awaiting BT to test) or perhaps the router ( Linksys WAG54GS) I am 99.9% sure my exchange is not being upgraded at this time
Any ideas chaps, how to resolve?
Cheers

[BliarOut]

ADSL is a contended service.... Chances are it's used more heavily in the evenings.

[scooby_snax]

It was equally as bad 6am this morning so I dont think that is the problem. In addition why would suddenly drop.

[Scraggles]

ran a virus killer or adware wiper recently ?

just ran speedtest on www.speedtest.bbmax.co.uk/
Download Speed: 6189 kbps (773.6 KB/sec transfer rate)
Upload Speed: 371 kbps (46.4 KB/sec transfer rate)

Seems ok

Maybe you are on a capped service with a FUP, i have neither, helps to provide more details...

[scooby_snax]

what is a FUP?
Whilst I am on capped service technically I guess things should improve tomorrow. I would have thought though I would have got a warning from my ISp

[scooby_snax]

I wonder if the 'day shift' can offer any advice?