The fact that the bond price has risen does not necessarily mean there is a takeover in the offing as bonds are not like shares. The rags bond offers about 8.5% interest per annum for 7 years. So if you buy £1000 worth, you get £85 a year for 7 years, then (in theory) get your £1000 back. So the bond is like a loan, on which you get a fixed sum of interest.
Bonds can be traded and the price will reflect a number of factors like how long is left to maturity and the underlying rate of interest in the economy. The latter is important as, all things being equal, you would expect the price to reflect the fact that you're getting a guaranteed £85 interest per year and your money back at the end of 7 years.
So if you bought these 1 year in, you would in theory pay something like £1350 for a £1000 bond as the money you'd get back after 6 years would represent 2% interest over that time on the original. If you bought them the week before they matured you'd only pay £1000 because that's all you'd get back. Clear?
The problem is that there's an element of risk with these as you're assuming that the rags will be able to pay the interest every year and the capital at maturity. That will depend very much on their financial outlook so a takeover by Qatar could help ensure that these will be repaid, thereby reducing the risk and increasing the price. But you will still only get your £85 per annum plus £1000 no matter how wealthy they are.