With regard to the new ruling of 10th August, it would appear that, where the applicant does not meet financial requirements, where there is a child in involved and where there are exceptional circumstances, the decision maker (ECO) can decide as to whether additional resources, such as third party support, can be used.
The following statement appears throughout the document I previously linked:
Require the decision-maker, where an application for entry clearance or leave to remain made or considered under Appendix FM does not otherwise meet the relevant requirements of the Immigration Rules, to go on to consider, on the basis of the information provided by the applicant, whether there are exceptional circumstances which would render refusal of the application a breach of Article 8 because it would result in unjustifiably harsh consequences for the applicant or their family. This
brings the test of proportionality under Article 8 into the Rules.
Therefore if you are thinking that you can get monetary resources from your Grandparents, but do not have exceptional circumstances and Article 8 reasons,I d not think this will apply.
As HKG3 says your grandparents or anyone else for that matter can 'gift' you what money you need already.