Can't get Redis memcache working on Ubuntu 18.04

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I can’t work out how to get the Redis memcache stuff working.

OS: Ubuntu 18.04
PHP: v7.2.24-0ubuntu0.18.04.4

So, I’ve installed redis:

apt install memcached
apt-get install redis

It seems to be running fine:

service redis-server status
● redis-server.service - Advanced key-value store
   Loaded: loaded (/lib/systemd/system/redis-server.service; enabled; vendor preset: enabled)
   Active: active (running) since Thu 2020-06-11 08:19:27 UTC; 40min ago
     Docs: http://redis.io/documentation,
           man:redis-server(1)
  Process: 22021 ExecStop=/bin/kill -s TERM $MAINPID (code=exited, status=0/SUCCESS)
  Process: 22048 ExecStartPost=/bin/sh -c echo $MAINPID > /var/run/redis/redis.pid (code=exited, status=0/SUCCESS)
  Process: 22025 ExecStart=/usr/bin/redis-server /etc/redis/redis.conf (code=exited, status=0/SUCCESS)
 Main PID: 22046 (redis-server)
    Tasks: 4 (limit: 4915)
   CGroup: /system.slice/redis-server.service
           └─22046 /usr/bin/redis-server 127.0.0.1:6379

Jun 11 08:19:27 pagething.com systemd[1]: Starting Advanced key-value store...
Jun 11 08:19:27 pagething.com systemd[1]: Started Advanced key-value store.

As per the docs, I’m trying to add this into /config/config.php:

   'memcache.local' => '\OC\Memcache\Redis',
  //'memcache.locking' => '\\OC\\Memcache\\Redis',
   'filelocking.enabled' => 'true',
    'redis' =>
      array (
         'host' => 'localhost',
         'port' => 6379,
      ),

Then when I try and run the admin panel, all I get is an nginx 500 IS error. i’ve tried finding the error log to tell me what the error is, but there seems to be nothing in there.

Any suggestions?

TIA

Andy