Cash accounting simplification is possible in UK. Businesses with an annual turnover below £1,350,000 can apply to account for VAT on all supplies when the payment is received. Similarly, input VAT is only claim on an invoice-paid basis rather than invoice received. One you are part of this scheme, you do not need to leave it until your turnover reaches £1,687,500.
More information on eligibility and application process can be found here.