A detailed answer would be huge. In brief......
See Pacey.org.uk for a run-down of the different types of childcare.
See childcare.co.uk or your local authority website's childcare database for an idea of what is available in your area, and to contact childcare providers.
The main differences between nannies and childminders are....
Childminders, in the true sense, have to be registered, inspected and regulated by Ofsted. Nannies do not, but some choose to be Ofsted-registered.
Childminders are self employed and, essentially, sell you a service under their chosen terms and conditions within the bounds of current laws and regulations. Ts&Cs may be negotiable to some degree. Nannies are usually directly employed by the family: you are their employer. This means you have more scope to lay down your own terms and requirements, but it also means you have more responsibilities as an employer: eg. employee's rights and benefits, minimum wage, payroll, pension, holidays, maternity benefits, etc.
Childminders work from their own homes. Nannies in your home.
Your 'other options' include....
Au pair. Usually a young person who lives with you and carries out some childcare and light housekeeping in return for board and a small cash allowance.
Private mutual arrangements with other parents/family/friends, with no cash payments or other reward. (These are notoriously unreliable.)
Babysitting. In a legal sense, this is really only babysitting if done in the evenings. Otherwise it falls into the next category, which is...
.... unregistered/unlawful/illegal childcare. This is anyone doing childcare for a bit of cash who should register with Ofsted but doesn’t. Roughly speaking, anything outside your home exceeding two hours for any type of payment or reward.