well phoned support....turned out I was trying the wrong file!! whoops!! feel a tad silly
I thought it was the .bin one but it wasn't, it was the 1.16 one.
But he did also tell me it works much better with the dsl cable out as well, if that is any help to anyone else.
Anyway, good news is I updated the firmware; bad news is is hasn't helped the original problem - my router is still getting masses of bandwidth usage when all devices disconnected. Have spent 3 weeks trying to sort it out with my ISP's help - firmware update was my last resort. I had narrowed it down to router issues as an alternative router connected has no such issues.
Looks like I'm going shopping.........