No. I think it would be the final nail in the coffin for them.
If they were 'online only', they'd be in direct competition with H Samuel and F Hinds. The only difference is, people know H Samuel and F Hinds because they're also in their High Street. Unless people already know about Gemporia, they're not going to be able to compete online.
The difference with Gemporia being on TV is that although their jewellery and prices are similar to those of H Samuel and F Hinds, their customer base will be different. The people that shop in H Samuel or F Hinds will be customers that are either specifically looking to buy jewellery - or people that have £50 surplus in their wallet, walk past the shop, see something they like, and think, "Oh, I quite fancy that and I've got that much in my purse - I'll treat myself" - and end up buying it.
Gemporia's customers are different. I doubt very much that people tune in SPECIFICALLY to buy an item of jewellery. I would imagine that most people have Gemporia on throughout the day as 'background telly', usually when there's nothing else on the TV. They'll look at the screen now and again, they'll see something they like and think "Oh, I like that - I'll buy it".
I don't think anyone tunes in to Gemporia thinking "I really want to buy a 9k gold Aquamarine ring with Tanzanite on the shoulders. I want it to have an oval main stone with round accent stones. Oh, and it must be between £200 to £200". Lets face it, if people wanted to buy something specific, they'd probably go to a jewellers that offers something more bespoke. This is why the Arthur Ivy collection and 'Museum' pieces don't work on Gemporia/Gem Collector. Do they seriously believe that people have a surplus £20,000+ in their bank account to spend on a 'spur of the moment' opportunist purchase?
If Gemporia was to switch to 'online only', they will lose those kinds of 'spur of the moment' purchase customers.
Not only that, but if Gemporia was to switch to online only, then their business model would change - and therefore, so would their prices. Gemporia on TV has the advantage of bulk selling 100 pendants in 3 minutes for the reasons stated above - people tune in, think "Oh I like that", and will buy it. They have thousands of viewers at a time. It's inevitable that some of those people will like it and buy it as a 'spontaneous' purchase.
100 pendants sat on a website would probably take days/weeks/months to shift. That means stock is tied up. That means higher prices.
So, no, I don't think it would work.
If they're struggling to sell now when they have thousands of viewers tuning in, then they'll certainly struggle when they have occasional website visitors.