As MrSaffron says.
You say the ISPs you have checked. I think both Sky and TalkTalk will do as he says and are offering only the "up to 38Mbps" product because of the 38.1 in the Clean
estimate, though both do have the 76Mbps one available. As a side issue I think the TalkTalk one is only 2Mbps upstream rather than the normal 10Mbps.
Have you looked at Plusnet or any other ISP? Plusnet may do the same, (38/20 in fact), but can easily be persuaded to give you the 76/20.
With any ISP your line can connect at the same speed as now as long as you are on the right product.
My broadband basic info/help site - www.robertos.me.uk
| Domains,site and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 57.1/14.8Mbps @ 600m. - IPv4BQM
"Angels can fly because they can take themselves lightly."
- G K Chesterton.