Update.

So my little Honda c90 is in the bike hospital getting repaired. I've decided against putting a foreign engine in the bike, I really want to do it on a Honda. And financially, with having to buy a spare engine that would fit from England and then having to ship it over here, the costs wouldn't equate in my favour with compared to having it repaired.
 I've managed to find a good garage and they say that the maximum it will cost will be 500 euro/£450, or less, depending on the amount of work involved. They said that really, it should cost more but with what I'm trying to do they are going to charge me less than what it should cost and try to keep the expenses minimal. They're really good people.

So to dispel any myth about what happened to my bike, this is the story of how I managed to break it...

About 50 miles South of Barcelona the odometer was ticking down to the time when I needed to change the oil. This would be the 5th time I've changed the oil in total, its something that I've done before and its always been fine. The thing that was different about this oil change however, was the oil itself. The Haynes manual, the book that's printed with the bike, recommends 20w50 oil - the oil that I've always changed it with and the oil that I took enough of with me from home for one change. I put in the last of the 20w50 oil in Northern France and since then I hadn't been able to find any. After scrupulous searches on the internet, sites such as The Honda C90 Club - http://www.c90club.co.uk/portal.php?sid=c93803997db47a2ed1a61b7e7c32357b
and maintenance sites such as this http://www.carlsalter.com/Honda-C50-C70-C90-maintanance.html I discovered that 10w40 oil should be okay, an oil that's readily available. So this is the oil I put in, right up to the correct level on the dipstick - well, when it was screwed in anyway, not placed in. The first mistake.
 So with a Honda c90 your meant to change the oil every 1000 miles. When the engine died I was in the 600 mile range, well within the comfort zone of when I needed to change the oil. The second mistake. I became complacent. I hadn't taken into account that 20w50 oil is a lot thicker than 10w40 oil, and that combined with the 30c temperatures of coastal Spain and the amount of miles I put in within a few long days at high rev's, I churned up the oil and ground it down way before the time I was used to.
 On my way to Ciudad Real I thought it best to pull over, fill up and give the bike a good looking over. I tightened and lubricated the chain and 'checked' the oil. By this point I was 500 miles into the oil since the last change and really didn't give it cause for concern. I pulled out the dipstick and it was covered in oil. 'Pa, its fine.' The third mistake. With knowing that the oil shouldn't need changing I just glanced at the stick, saw it was covered, didn't bother wiping it and just put the stick back in. I made this same mistake again when I set off on the day that it broke down, assuming I was in the safety zone of an oil change and thinking that the stick was covered in oil.
If I was more vigilant, spent a few seconds checking properly, I would have saved myself £100's, a lot of shame and spared myself a lot of depression. But it happened, the oil became churned up in a shorter time than I was used to, I didn't check properly and the engine has seized. Its a massive disappointment that its happened but I can't change it now. There's no point in pissing and winging about it. I made a mistake, well several, and its cost me some money. £450 is a lot to have to fork out so soon on the trip, but if it has to be done to continue then its just a little blip in the grand scheme of things. This journey is priceless, and as my friend, Kelly Parish once said when regarding financial decisions, 'There's always more money to earn.'

The bike should be ready within a week and then I'll be on the road again. The old hands at the garage are adamant that when they've finished with it, it will get to South Africa. I hope so.