>>>> Inspection of the closing prices(the ones I use) before and after the Dividend Date shows there is hardly any difference in actual prices. <<<<<
The dividend is paid quarterly and the annual yield is about 1.5% so the change in price due to the dividend each quarter is not that great.
I know if I am AIMing I just dump the dividends in to CASH and let AIM decide when to use it but for testing purposes you need to account for it consistently somehow.