PHP / WordPress Expert to integrate a custom PayPal Subscription

General information for the website: Membership Website
Kind of development: Customization of existing website
Description of requirements/features: I need to have a custom PayPal subscription service setup on a website I am building. There are several complex points which I'll try and explain below:


I have several custom user roles setup on the site and these custom roles are for 'Members'. These members need to pay a yearly subscription fee. Different members (depending on user role) will have to pay a different yearly fee.
The yearly fee will be taken at the beginning of each year.

During several different date ranges of the year, the initial fee will be different. This is a pro-rata based subscription. I can tell you the exact dates and costs if you are successful, but there are 4x date ranges.

Also, each members' user role needs to be updated/upgraded to another user role on successful payment.
For example, I have a custom user role of 'provisional_member' which means they only have limited access to the website content, but upon payment via PayPal, they'll then automatically become 'general_member', which grants them access to the hidden content.

There are 14 custom user roles setup. 7 prefixed with 'provisional_' and then 7 prefixed with 'general_'.

Recap:
1) Users get an account setup for them manually,
2) Depending on the type of account they sign up for, they will be granted a 'provision_' user role,
3) They pay via PayPal a percentage of a yearly fee upon initial payment,
4) Then each January, they pay the full yearly fee (again, depending on user role, the fee will be different),
5) Once the initial pro-rata payment has been made, they get upgraded to a 'general_' user role.
6) If the payment is unsuccessful, then their user role gets downgraded back to 'provisional_' again.

I am looking for someone in the UK, if you're not from the UK please do not send a proposal. I need this done fairly quickly also I'm afraid, please let me know if you can do it soon.

Please feel free to ask any questions if something is not clear as this is a little complicated!
CMS and Admin requirements: WordPress Based Custom Built Theme
Extra notes: