What's important to you? Would you want to spend as little as possible but then be at the mercy of it slowing down a bit in the evenings? Or would you prefer to spend a few more pounds to ensure it's always quick and snappy, even at 8:30 on a Sunday evening?
What time of day & day of week is your usage? EG is there very little / no usage during the 9am-6pm period Monday-Friday? Or are you likely to be on at any hour?
Was on Xilo C&W LLU on MRCEN, Now Be* on MRARD.