Ok, so recently they have double data, but just a week before I had a contract with Virgin paying £23pm for unlimited everything. Since then I got contacted advising if another line was taken out it would be offered on 4G internet at: £12.50pm for 6 months on a 30day rolling contract.
£12.50 (6months £25 there after)
20gb Data (dont know if they give 40)
2000virgin to virgin
As they dont upgrade existing contracts, below is step to keep number and only have 1 line.
Take out additional line with Virgin at 12.50
Get pac code for existing number
Transfer to Three
Once number transferred to three, get pac code and move back to virgin giving new pac code from three to virgin on new sim
Note: Three cant generate pac code instantly if you request in there 14day cancellation period, to avoid this get a 30day rolling contract when switching or alternatively move number to payg sim but it might take longer.
Only available by ringing through to sales team
Network for 4g is LTE
Speed test on iphone7plus: http://www.speedtest.net/my-result/i/1870785627