280kts is fine if we de-restrict you, but if we ask you to keep your speed up in the descent, then we would appreciate you doing just that.
As for no speed on climbout, then we have no speed restriction, it's up to fly whatever is best for the a/c or SOP's etc.
Also depends on the class of airspace you're in, in a known controlled airspace environment (Classes A-D), then the see and avoid principle does not apply, however in Class E airspace (Mainly the Scottish TMA around Glasgow and Edinburgh), then you will transit from class D (Known) to class E (unknown) controlled airspace where the see and avoid principle applies, as does the 250kts speed limit.