Didn't know about that, thanks, so what is the minimum length time? 
Normally a fortnight. Plus any intervening Bank Holidays. In Ofcom speak, 10 working days, where working days are Mon-Fri 9am-5pm.
GC 22.30 (rr) “Transfer Period” means a period of 10 Working Days before a Customer’s order can be activated;
GC 22.30 (uu) “Working Day” means the hours between 09.00 – 17.00 on Monday to Friday, with the exception of Bank Holidays;
Ofcom General Conditions.
My broadband basic info/help site -
www.robertos.me.uk. Domains, site and mail hosting -
Tsohost.
Connection - AAISP Home::1 80/20. 200GB. Sync 74145/13476Kbps @ 600m. BQMs -
IPv4 &
IPv6