I was thinking about relativity (as one does) and this question came to me: Has there ever been an experiment which has tried slowing down an object relative to us to see if time speeds up?

At one time an atomic clock was placed on a plane in order to measure the time dilation effects. The moving clock was running slow compared to the a clock of the same construction which was at rest. When the plane lander the clock went back to "ticking" at the same rate as clocks which are at rest. You're really asking whether clocks at rest run faster than clocks in motion. Since clocks in motion run slower than clocks at rest, it directly follows that clocks at rest run faster than clocks in motion. Simple, huh?

Is there a theoretical location (may be between galaxies) where an object could be slowed to be absolutely stationary where time is infinitely fast?

No. In essence what you're looking for is a clock that runs infinitely faster than clocks at rest in an inertial frame in flat spacetime where clocks run at their normal rate. If a clock is placed in a gravitational field at a higher gravitational potential than the zero level then that's the only way known to get a clock to run faster. To have it run infinitely faster the gravitational field would have to be infinitely strong and there is no such field where that's possible.

I have always thought of time as just a something which measures a number of changes comparatively.

Essentially that's about right. For a full treatment on time pleas see

http://users.wfu.edu/brehme/time.htme.g. a year is a rotation of the sun by the earth, or a day is a rotation of the earth (approximately) That means in these cases it is also a measure of distance like a light year. A second is a day/86400 so it the period for this rotation but it is also the period that a atom vibrates x times or the period it takes an element to warm up h degrees under the effect of t units of heat. Does this mean that travelling at the speed of light will stop all change, chemical, physical, electrical?

Questions like that need to be asked with a reference frame in mind since velocity is a relative concept. And a frame of reference does not exist in which instruments can be placed at rest in which travels at the speed of light.

Following from 2: chemical change, physical change etc all require energy. Does that mean that there is an absolute limit to the amount of energy that can be expended in a period.

The rate at which energy is used is called power and measured in units called Watts. There is no known practical limit to the how fast energy can be used.

Following Supplementary 3 would that make a mathematical relationship between energy and time or have I just come back to y=mc 2?

I'm sorry but I don't understand your question.

From 3: Does time stop in a black hole?

If you're talking about what happens in a frame of reference which falls into a black hole then at the origin of that frame of reference time runs at the normal rate.

Following from 2. If space is just a change in location and this takes time surely it is not surprising that space and time are related. Is this circular thinking?

No. But it's not correct. Space is not defined as a change in location. See

http://users.wfu.edu/brehme/space.htmWould it be possible to speed up a computer by sending into space and is this viable?

In space the gravitational potential is a tad bit smaller than it is on the surface of the ground. That implies that time runs tiny bit faster far from the Earth.

it really is keeping me awake at night.

Good man. I know the feeling. Been there, done that. :)