Do for the berries
Kids would traditionally pick Raspberries in the school summer holidays. As they wouldn't want to wear their best clothes but didn't want to look 'un-cool' in front of their mates they would wear their old, worn designer gear ie: I wouldn't wear it to the cinema but it'll do for the berries. Now used for the type of bird that isn't the best but won't cause embarrassment in front of your mates.
'What do you think of her over at the puggy?'
'She'd do for the berries'
'Aye, I'll give her a shotty'
'She'd do for the berries'
'Aye, I'll give her a shotty'