It's an absolute joke that there are no symmetric consumer-grade FTTP options from OR.
No, it's not a joke. It's market forces in action.
If you really need (or want) symmetric 1G/1G, you can have it now: buy a leased line. Expect to pay upwards of £300 per month, depending on where you live. It's definitely available to most of the UK, from a range of providers and networks, although there may be one-time excess construction costs to pay too.
What you're
really saying is: you want 1G/1G symmetric, but you want to pay much less (let's say, more like £50 per month).
There are good reasons why most commercial ISPs don't want to make that offering to you.
1. Most customers object to usage caps, more than they object to asymmetric speeds.
If they were to offer 1G/1G with no usage cap, then there would be people who would fill it 24x7. And they would have to sell such a service at a much higher price to accommodate that usage (or sell it at a loss).
If they were to offer 1G/1G with a usage cap, almost nobody would take it up - and therefore there's point providing it.
2. Download usage doesn't tend to vary much with speed.
That is: if you give someone a 1G download link instead of a 300M link, they'll likely download the same amount of data, just in a shorter amount of time. They still have to make use of that data: there are only so many games you can play in a day, or 4K UHD videos you can watch.
However, uploading tends to have a different usage pattern. If you are a P2P seed node, then you will fill your upload capacity 24x7. If you are doing regular non-incremental backups, you can fill your upload capacity. If you host your own website and it becomes popular, it can fill your upload capacity.
Therefore, limited upload speeds act as a sort of brake on abuse, without actually giving usage caps or AUP limits. A consumer ISP can probably cope with a few users each filling 100M 24x7; it's much harder to cope with the same number of users filling 1G 24x7, when they're still only paying low cost residential rates.
3. Linked to these is revenue protection. Openreach and Virgin Media both have large leased line businesses, with people paying good money for 1G/1G business grade uncontended links. Some of those would downgrade to a lower-priced 1G/1G contended service if it were available.
It's therefore in OR and VM's interests to differentiate these products, and upload speed is one key way.
Remember though that market forces are in still play. If there were
many people like this who would choose the lower-priced product, then there's an opening for a new entrant to challenge the encumbants with a more attractive offering. And there are a few. In practice though, most ISPs don't want to take on this sort of customer with a high-speed, low-cost product, for the reasons listed above: there's too high a risk involved.
4. People are more cost-sensitive than you think. Given a choice of a 1G/1G product at £60 per month, or a 1G/100M product at £50 per month, the vast majority of users would take the £50 product. Given almost no customers would take the 1G/1G product, there's no incentive for it to be provided, unless it's at the same price as 1G/100M.
Of course, there are a few exceptions. Providers like Vodafone on Cityfibre are happily offering 1G/1G products on GPON (despite the fact that GPON only has 1.2Gbps of upload speed, shared between up to 32 users). That's because they are desperate to take any market share they can, and will accept the risks in return for gaining a few tech-savvy customers with heavy usage.
However as outlined above, Openreach and VM have strong reasons
not to do this. Since the proportion of customers who care about upload speeds is very low, they know they will only lose a small number of customers this way. In the big picture, having better control over the remaining customers, and protecting their leased line revenue, is far more important.
As for XGS-PON: this is a technology, not a product. Even though Virgin Media is deploying it, that doesn't mean they'll ever offer symmetric residential services: that will be entirely a marketing decision.