“Whilst, as noted above, the claims process is experienced as straightforward for the majority, it emerged strongly that the five week wait for the first payment was particularly difficult for those with housing costs, and this is reflected in the relatively high take up of the UC advance at Wave 1, compared with other forms of financial support”.

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/481865/universal-credit-extended-gateway-evaluation.pdf

hbinfo note: this finding by the DWP is surely critical. Landlords just will not wait this long when market rents are already well above HB levels.