Yeah I'll try it tomorrow at my sister's if it works there it's the signal at mine isn't it but if it still struggles then it's the boxthe router has good SNR and the box doesn't, you could try a signal booster but they're about £20 and it's not guaranteed to work in your case.
it could be a faulty tuner...is there any chance you could take it to someones house with VM and check it there?