I was recently issued with a U.K. Standard visitor's visa. It's valid for 6 months and multi-entry. When I applied, my intended travel dates were in December. However with new family developments I am unable to travel in December. My purpose for traveling to the U.K. hasn't changed, nor has the duration, the only thing that has changed is the date. Would I have problems entering the U.K on a changed date that is still within my visa validity?
Since you journey is still within your visa validity period, another entry date will not be an issue. You can enter and leave the country between two dates printed on your visa - "valid from" and "valid until".
And entry date is not printed on the visa anyway so no one would even know that your planned arrival date had changed.