What i would be concerned about is the tax and NI purposes. If they are notifing the inland revenue that you are earning �43,254 a yr rather than half of that then this is a concern. Firstly i would call the National Insurance helpline. Ask them if they can let you know if your NI stamp has been paid over the last 3 months. Their number is 0845 302 1479. Give them your NI number. if it has been paid, check the amount they received from your employer. You can compare that then to the payslip and the BACS amount received (after deductions).
Also, do they do their own payslips or do they use a payroll outsourcing company. i.e Ceridian Centrefiel for example ? (is in in-house basically?)
Let me know what NI helpline say and i will let you know what to do next...