combo bubble plot

Hi all

I recently took part in a fauna survey of a meadow, where we reviewed one 1m square sites in a number of locations across the meadow to assess its health.

I would like to present this data using the actual X and Y coordinates of the survey points and then have some representation of the over all health at that point. I thought a good way to do this would be using a bubble plot. With the coordinates being the X and Y and the health being the size of the bubble. That way we could get a visual representation (map) of the health across the site and potentially be able to compare future surveys be adding other data series for other surveys . The idea being that this might help us understand if some areas of the meadow healthier than others eg northwest corner or how things change over time.

To help make this clearer I would like to do a couple of extra things to the chart and I just wondered if someone could given me a steer on how to do the following if possible:

1. I would like to draw the meadow boundaries onto the same plot using the x and y coordinates so either using a scatter or line plot. So this would require a combo of scatter/line and bubble is this possible unless I can connect a separate series of bubbles with fixed size of 1% with lines. From a response in the Questions area it has been proposed that I grab a screen grab of another chart and use this as a background. which might make aligning difficult . So can I suggest that it might be worth looking at is this might be a future development
2. Is it possible to get the actual bubble to colour code on the values in them ie RED if health under 30% to green if heath over 80% so that it is even clearer which are the healthier meadow areas. The proposed answer to this was to split the data into series for plotting with each series having a designated colour. Which works but would make plotting future years on the same graph difficult.