In 2017, the rate for businesses/sole traders that spend <2% of their income on goods changed to 16.5%, probably because the government felt the 12.5% was giving too much of an advantage.
16.5% is only a tiny amount less than the "normal" VAT rate, as it's calculated on the total invoice amount - for an invoice with a base cost of £100+20% VAT, you'd bring in £120 and pay out £19.80 to the government. If you used standard VAT accounting, then you'd pay out £20 to the government and be able to reclaim VAT on any goods you did buy as part of the business. If more than 1% of your income is going on goods, you'd be better off with the standard approach.