Off peak speed is capped

[#1]

I've gone over my usage allowance (no surprise) and have been throttled down to pre-broadband speeds during the day time.  I was under the impression that this would only happen during peak times though.
This is a speed test at 00:46 this morning.
Today 00:46 120 kbps (15kB/s) 75 kbps (9.38kB/s)

Shouldn't I still get full speed off peak?

[#2]

I've just updated my allowance to 40gb and saw an immediate jump:
Today 01:05 33964 kbps (4.25MB/s) 8275 kbps (1.03MB/s)
Does the rate limit affect the speed at all times of the day?

[#3]

Yes it does