The cooling fans can get noisy if they get clogged. If this is the main issue, run a vacuum cleaner around the outlet & it may clear the issue. If not then call faults. Sluggish responses can be caused by signal issues as well as box issues.
Cable customer since 1993. Services: FH TV, Sky Sports & Movies (2xV+), Talk Unlim Telco, VIVID 100, Virgin PAYG Mobile
Thanks for your post and I'm sorry to hear the V+ HD box is really noisy.
I can see nodrogd has already offered some advice around this which is greatly appreciated. Did you manage to give the vents a little clean as suggested and has the noise improved? I would have had a quick check over the box for you but I'm having some difficulties locating your account details. If you're still having trouble I can certainly take a further look at this for you, just let me know.