Permissions Error

I have a wordpress site running on fluxlondon.co.uk. It has been fine for months but is now showing the following errors:

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Warning: unlink(/home/domains/vol2/943/1293943/user/htdocs/wp-content/uploads/bb-plugin/cache/2-layout.css): Permission denied in /home/domains/vol2/943/1293943/user/htdocs/wp-content/plugins/bb-plugin/classes/class-fl-builder-model.php on line 707

Warning: unlink(/home/domains/vol2/943/1293943/user/htdocs/wp-content/uploads/bb-plugin/cache/2-layout.js): Permission denied in /home/domains/vol2/943/1293943/user/htdocs/wp-content/plugins/bb-plugin/classes/class-fl-builder-model.php on line 707

Warning: unlink(/home/domains/vol2/943/1293943/user/htdocs/wp-content/uploads/bb-plugin/cache/23-layout-partial.css): Permission denied in /home/domains/vol2/943/1293943/user/htdocs/wp-content/plugins/bb-plugin/classes/class-fl-builder-model.php on line 707

Warning: unlink(/home/domains/vol2/943/1293943/user/htdocs/wp-content/uploads/bb-plugin/cache/23-layout-partial.js): Permission denied in /home/domains/vol2/943/1293943/user/htdocs/wp-content/plugins/bb-plugin/classes/class-fl-builder-model.php on line 707

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The error is in the beaver builder plugin. If I try to update any plugin or wordpress version I’m asked for ftp credentials which I haven’t had to do before. I put in the credentials but the update fails and my site goes into maintenance mode.

Any help would be much appreciated.

Thanks