Getting it going on a MySQL db [Via Docker]

Many apologies if this is a real noob question - hopefully I’m just missing summat fundamental.
But I’m just getting going with grafana; I have a MySQL db that is populated with data from a number of sensors. The db is all good - I already have a simple php page that dumps the rows.
I’ve added the [local] mysql server as a data source, and it checks out ok with the “Save & Test”.
My db (“sonnet”) has this table:

CREATE TABLE `Measurements` (
  `MAC` char(16) NOT NULL COMMENT 'Node Address',
  `Time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `Temp` decimal(3,1) DEFAULT NULL,
  `RH` tinyint(4) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

I’m trying to get started with just a Singlestat dashboard; I’ve selected my Data Source, set “Format As” Table; with the following SQL:

SELECT
  UNIX_TIMESTAMP(Time) as time_sec,
  Temp as value,
  'Tempe' as metric
FROM Measurements
WHERE $__timeFilter(Time) AND MAC='00158D00001180FE'
ORDER BY Time ASC

But when I click on “Query Inspector”, it seems to come back with

xhrStatus:"complete"

request:Object

method:"POST"

url:"api/tsdb/query"

data:Object

from:"1533632362593"

to:"1533653962593"

queries:Array[1]

response:Object

results:Object

A:Object

message:"dial tcp 192.168.10.67:3306: connect: connection timed out"

Any help please on where I might be going wrong? In case it’s relevant, I’m running this all in a Docker Container on a QNAP/QTS NAS. (The MySQL server is outside the Container - but the “Save & Test” suggests it’s connecting to it ok?)
Thanks

Follow up: Ok, so the “Save and Test” isn’t in fact working (I wasn’t waiting long enough… :S)
So my issue seems to be getting Grafana-in-a-Docker connecting to the system’s ‘native’ MySQL server - not sure if the Docker Container needs some re-config of networking…?