Ubasses, is as usual, on the money.
Technically, flowers and a wake are not a valid testamentary expense. Although if I were feeling clever I might try and argue that they come under "mourning expenses".
Yes Juniper should ask the executor, but realistically the executor should ask the residuary beneficiaries. MOST beneficiaries wouldnt have a problem with this, but some national charities are known to be particularly parsimonious.
Juniper runs the risk (if he/she is not the executor) of funding these expenses and then not having them paid from the estate.
I would suggest that Juniper's friend makes a short codicil bequeathing £** to JuniperEccles for the purposes of providing for flowers and a knees up (in addition to anything else JuniperEccles may be bequeathed).