But keep in mind that, unlike in the US, if you conceive shortly after beginning a new job, the employer is NOT obligated to pay your maternity leave. You must have been working with your employer for 26 weeks by the 15th week before your baby is due. You can still claim Statutory Maternity Pay at £108/week, but this may be far less than a full-time (or 80% of your) wage/salary. Also keep in mind that probation periods vary in the UK - many are 6 months. And an employer can terminate you for any reason during that time. Not pleasant to have to think of these things, but practical issues nonetheless.
Also, the NHS is not 'free', you pay for it out of your earnings.