LONDON, Oct 7 (Reuters) - The battle to hold a second Scottish independence referendum moves to Britain's top court next week when it hears arguments for allowing a secession vote in a year's time without approval from British Prime Minister Liz Truss and her government.The UK Supreme Court is being asked to decide whether the semi-autonomous Scottish government, led by the Scottish National Party (SNP) with support from the Scottish Greens who also back independence, can push ahead with plans to hold a referendum without the consent of the British parliament.Polls suggest the outcome of any vote on whether to break Scotland's three-century-old union with England would be too close to call.Sturgeon argues that as voters backed pro-independence parties in elections for the Scottish parliament last year, there was a mandate for them to bring forward a bill to hold a referendum on Oct. 19, 2023.She said next year's vote would be consultative, not self-executing, and would require further legislation from both the UK and Scottish parliaments for Scotland to become independent."