Both could just be the result of normal sample error. (yougov.co.uk)
I'll urge my usual caution about polls showing movement — sure, it could be the start of a trend, but it could also just be normal sample error. (ukpollingreport.co.uk)
The difference between the national picture and the marginal picture will normally be so subtle that it could easily be lost under or mistaken for normal sample variation, or the methodological differences in doing marginal polls (or vice-versa, normal volatility or methodological impacts could be mistaken for a different pattern in the marginals when there is none). (ukpollingreport.co.uk)