You've chosen to go with a cheap no frills ISP which uses a cheap no frills router that no doubt meets the requirements of >99.9% of the users of that ISP. Now there's no reason not to go with a cheap no frills ISP but given you choose to run a server from home then it's up to you to purchase and use a router/modem that meets your needs rather than (repeatedly) complain that the supplied cheap as chips router doesn't meet your needs. That the earlier TG582N router modem supported NAT loopback is irrelevant, the current model apparently does not is what matters. Unfortunate, yes, but not something that the vast majority of its users require. Similar problems exist with other ISP supplied routers, for example BT's current SmartHub doesn't, as far as I know, respond to pings and therefore can't be used with the likes of TB's Broadband Quality Monitor.

I've got a router that meets my needs, just awaiting details, so I can use it!

I'm not complaining; I was just trying to establish if the TG588 does what the TG582 does or not. Most importantly I was trying to get technical details, which I think should be supplied by the manufacturer, or failing that might be known by folk on here. I thought that was the whole idea of the forum?