Competition to attract savers’ Isa cash is heating up, with a building society launching a new rate described by a savings expert as market leading. Skipton Building Society has launched the 18-month fixed-rate cash Isa at 4.55% AER (annual equivalent rate). The society said the account is available to both new and existing customers and can be opened online, using the Skipton app, in branch or by phone. The minimum balance in the account is £500, with a maximum of £1 million. Customers can deposit up to their annual Isa allowance of £20,000 and transfer in Isa savings from previous tax years if they wish. Savers need to bear in mind that withdrawals are not permitted during the term and early closure is subject to a 90 days’ interest penalty.…