A: You are required to pay national insurance up until state retirement age if your annual earnings are above the small earnings limit of £5,435. If you don't expect your locum income to exceed this amount, you can apply for exemption from paying class 2 national insurance: the form can be found at www.hmrc.gov.uk
When you retire from the partnership you will be paid the balance on your capital and current account (the funds you have invested in the partnership). This will be calculated when the final accounts are prepared. Whether you are owed any further money will depend on your final balance. It is not possible to give a definite answer without seeing. I suggest you contact the practice accountants.
The balance on your current account reflects your share of total assets and therefore there would not be an additional payment to you for fixture and fittings. If you own a share of the premises, this would normally be re-valued at the date you are retiring.