New investor questions; CGT (Capital Gains Tax)/Share taxes

Having dipped my toe in PM & not stopped until I am waist deep, I have had to look into the tax situation promptly!

As a basic rate tax payer, on the shares front, am I correct in saying that I pay no tax on the first £5000 per annum of share dividend?  As I understand it this applies to the rent/'interest' paid by the SPVs.  My understanding is that on completion of the term, in most cases the shares will be sold & thus payments are liable to CGT not treated as dividend.  www.gov.uk/tax-on-dividends/how-dividends-are-taxed

Moving on to CGT, wow, what a learning curve!  My first observation is that the statement downloadable on PM is not sufficient, being as labelled on a FIFO (first in, first out) basis, where it is much more complicated!  My understanding is that I do not pay CGT on the first £11,100 per year.

My understanding here is that shares in the same SPV are taken as average cost (including secondary market fee where applicable) over all shares owned when deciding any profit liable to CGT, with two overriding factors;

• Any shares bought on the same day are treated as being sold first (even if perhaps bought later than the sale)
  
• Any shares bought in the 30 days immediately following the day of purchase (again despite being bought after the sale), with the caveat that the seller must be UK domiciled for tax purposes at the point of sale.
  

www.gov.uk/government/publications/shares-and-capital-gains-tax-hs284-self-assessment-helpsheet/hs284-shares-and-capital-gains-tax-2016#how-you-work-out-the-gain-under-the-bed-and-breakfasting-rule

The obvious question here is how the heck do I know the tax status of the seller when via the secondary market I don't know who they are (presuming that PM don't buy & then sell the share to me)?  Am I safer to assume that they are or are not if I don't know?

For example I invest (primary investment) at £10, sell at £10.25, then within 30 days buy back for £10.20 (including 2% PM SM fee), my understanding is that 'bed & breakfasting' rules benefit me by reducing the amount exposed to CGT from 25p (the actual profit I made at the point I sold) to 5p (the net profit I made when instead calculated against the re-purchase cost after fee).

I want to do a spreadsheet to monitor my position (I will be happy to use the £1,100 of my allowance, I just want to be sure that I know where I am).  This 30 day malarkey makes it fun - what if I buy & sell the same shares twice in 30 days?

I appreciate any advice.