cant see a problem with draining and reusing the oil - even if you buy brand new perfectly clean bucket and then bin it afterwards it wouldn't be more than a fiver, certainly cheaper than fresh oil.
Actually starting to think i could take off the oil filter and current sandwich plate, they're higher than the oil pan so can probably get away without losing that much oil.
Then i've got spare oil to top-up to the correct level after.
Ordered a SPA digital gauge
http://www.spa-uk.co.uk/Category/Digital%20Gauges
Now just need to workout the correct sandwich plate to order, would be great to get one that my goodridge hoses and the temprature gauge plug direcly into.
Please talk on the forum about piggybacking two.