mmm. Funny thing. I'm really not sure this is Hartley Wood, personally. It's mould blown and has a machine cut rim, neither of which are common HW characteristics. Then there's the colour and patterning, which aren't particularly HW either - this company was connected to the production of stained glass - swirled, brighter and more vibrant transparent colours are more usual. I can't recall when the factory closed, and I'm away from my library right now.
Handmade (hand moulded/blown) forms are also more typical for HW, most somewhat charmingly uneven. I've not seen a piece of HW in this globe form before either. I'd almost have suggested Guernsey or one of the Maltese factories you mention, were it not for the cut rim and mould blown nature - as you say. The colours are wrong for Royal Brierley Studio, although the shape and manufacturing technique are nearly there. However, I'm not sure what HW's FULL 1980s range included, and the tag does say 'giftware'....
I'd be very surprised if it was HW, but have seen enough about new and under-researched areas to know one should never say never. A last attempt at commercial success with a range of mould blown giftware perhaps? It is possible.
I'm out. Any other suggestions? I'd like to know myself!
Best,
Mark
P.S.; Is there a band inside of the rim that has been ground down, leaving it slightly rough? If so, there's certainly a missing stopper.