Depends on what you are meaning by "LLU".
Do you just mean "Full LLU" where your ISP provides both BB + phone line, which your Sky probably is? Then the only other ISP is TT; + maybe some resellers.
Or do you include "Partial LLU" where the ISP provides the BB and someone else, usually BT, owns the line? Many ISPs do this at selected exchanges.
You usually get faster throughput from LLU ISPs, when they are active at your exchange.
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU BB => 2010: Orange 19 Meg Tweaked / 16 Meg Untweaked LLU BB