Never seen a comma used in Britain, during my almost sixty years as a native. It's usually £1.50 (and yes, a central dot not a period unless typed), occasionally £1-50 which is most commonly seen on shop and handwritten market signs.
Pre decimal was almost always a '-' when there are pounds, a / (more like a super long apostrophe) when under 240p. So £5-2-6 for £5, 2 shillings and sixpence, 7/6 for seven and sixpence. Less common was £5 6s 2d, or slashes £2/19/2 3⁄4d, but there were a lot of conventions for written Lsd, with nary a comma among 'em. :)
Edit: to your edit, = was common (seems much less so now) for whole pounds, and in the pre-decimal era too, e.g. £1/==, or simply £1==. Also pre decimal whole shillings: 5/=, sometimes 5/-. In the days we still wrote cheques when it was for whole pounds it was common to fill the remainder of the figures box with two lines, essentially =====, after the £250 or whatever numerals.